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STEAM-BOILERS. 



BY 

CECIL H. PEABODY and EDWARD F. MILLER 

Professor of Naval A rch itecture Professor of Steam 

and Marine Engineering, Engineering, 

Massachusetts Institute of Technology, 



SECOND EDITION, REVISED AND ENLARGED. 
FIE ST THOUSAND. 



NEW YORK : 

JOHN WILEY & SONS. 

London: CHAPMAN & HALL, Limited, 

1908 



1* 



LIBRARY of CONGRESS 
Two Copies Received 

OCT 26 1908 

Copyright Entry 
CLASS Gu XXc. No, 



Copyright, 1897, 1908, 



C H. PEABODY and E. F. MILLER 



3l 



5> 



Sty* 0riPttJifit $rau 
fUibert Irumraoni anii CEIompattu 






PREFACE TO FIRST EDITION. 



In this book we have attempted to give a clear and con- 
cise statement of facts concerning boilers, and of methods of 
designing, making, managing, and caring for boilers. Though 
the book is intended primarily for the use of students in 
technical schools and colleges, it is hoped that it may be 
found useful to engineers in general. 

There is given a description of various types of boilers in 
common use. Following this is a discussion of combustion, 
corrosion, and incrustation, with a statement of the most recent 
investigations and conclusions on these important subjects. 
We are fortunately able to give a satisfactory table of the 
compositions of American fuels — the first, so far as we are 
aware, that has been published. 

A statement is given of the proper and of the customary 
sizes and form of furnaces, and of the methods of firing. In 
the present unsatisfactory condition of the chimney problem 
we have contented ourselves with giving the ordinary theory 
and pointing out its defects, together with the common ways 
of proportioning chimneys. 

Tables of grate-areas and heating-surfaces, and of other 
proportions of furnaces and boilers, have been made up from 
the oest current practice for stationary, locomotive, and 
marine boilers. 

In the chapter on strength of boilers we have given briefly 
the methods and conditions for testing materials and for 
making boilers, and the properties which such materials 



IV PREFACE. 

should have. Especial attention is given to the properties 
and proportions of riveted joints, deduced by Professors 
Lanza and Schwamb from tests at the Watertown Arsenal. 
Simpler calculations of stresses in the members of boilers are 
explained, and more complex ones, depending on the theory 
of elasticity and theories of beams and continuous girders, 
are illustrated by examples. 

A description is given of staying and other details affect- 
ing the design and construction of boilers, and of such acces- 
sories as safety-valves, gauges, and steam-traps. In order 
to give a conception of the methods and conditions of boiler- 
making, we have given a description of a modern bciler-shop 
and the machinery and processes used in it. 

In the chapter on boiler-testing we have given the 
methods used in the laboratories of the Massachusetts Insti- 
tute of Technology, including gas analysis, measurement of 
air used, and temperature, determinations in the furnace and 
chimney. 

Finally, the principles and methods set forth in tr e earlier 
chapters are brought together and illustrated by applying 
them to the design of a boiler of a common type. For our 
own students this chapter serves as an introduction to a 
course in machine design given by Professor Schwamb, who 
has kindly furnished us with methods and materials which he 
has collected and developed in connection with the design- 
ing of boilers. 

In the appendix are given various useful tables, such as 
logarithms, natural trigonometric functions, areas and circum- 
ferences of circles, proportions of rods and screws, and proper- 
ties of saturated steam C. H. P. and E. F. M. 

Boston, February i, 1897. 



PREFACE TO SECOND EDITION. 



A considerable amount of new material and many new 
illustrations have been added in the Second Edition. 

While but few changes have been made in the treatment of 
the subject, each chapter has been added to and revised. 

A short chapter on Superheaters has been added; also a 
number of tables giving the dimensions of and the floor space 
occupied by the different types of boilers and by economizers. 

The subject of steam-piping has been treated at greater 

length. 

C. H. P. and E. F. M. 

October i, 1908. 



CONTENTS. 



CHAPTER I. 

PAGE 

Types of Boilers - i 



CHAPTER II. 
Superheaters 37 

CHAPTER III. 
Fuels and Combustion 47 

CHAPTER IV. 
Corrosion and Incrustation 75 

CHAPTER V. 
Settings, Furnaces, and Chimneys 101 

CHAPTER VI. 
Power op Boilers .... 143 

CHAPTER VII. 

Staying and Other Details 153 

vii 



viii CONTENTS. 

CHAPTER VIII. 

PAGE 

Strength of Boilers 178 

CHAPTER IX. 
Boiler Accessories 252 

CHAPTER X. 
Shop-practice , 304 

CHAPTER XL 
Testing Boilers 333 

CHAPTER XII. 
Boiler Design 360 

APPENDIX 395 

INDEX 421 



STEAM-BOILERS. 



CHAPTER I. 

TYPES OF BOILERS. 

Steam-boilers may be classified according to their form 
and construction or according to their use. Thus we have 
horizontal and vertical boilers, internally and externally fired 
boilers, shell-boilers and sectional boilers, fire-tube and water- 
tube boilers: the several features mentioned may be combined 
in various ways so as to give rise to a large number of kinds 
and forms of boilers. Again, we have stationary, locomotive, 
and marine boilers, together with a variety of portable and 
semi-portable boilers. Locomotive boilers are always shell- 
boilers, internally fired, and with fire-tubes ; and the re- 
strictions of the service have developed a form that has 
changed little from the beginning, except in the direction of 
increased size and power. Marine boilers present a much 
larger variety of form and construction, depending on the 
steam-pressure used and the size and service of the vessel to 
which they are supplied. The Scotch or drum boiler is more 
widely used than any other form at present, but the tendency 
to use high-pressure steam has led to the introduction of vari- 
ous forms of water-tube boilers for marine work. The variety 
of forms and methods of construction of stationary boilers is 
very wide : each country and section of a country is likely to 
have its own favorite type. Thus in New England, where 



2 STEAM-BOILERS. 

the water is good, cylindrical tubular boilers are largely used; 
in some of the Western States, where water contains mineral 
impurities, flue-boilers are preferred; and in England, the 
Lancashire and Galloway boilers are favored; and again, 
various forms of sectional and water-tube boilers are now 
widely used. 

Cylindrical Tubular Boiler. — This type of boiler is shown 
by Figs, i and 2 and by Plate I. It consists essentially of a cylin- 
drical shell closed at the ends by two flat tube-plates, and of 
numerous ftre-tiibes, commonly having a diameter of three or 
four inches. About two thirds of the volume of the boiler is 
filled with water, the other third being reserved for steam. 
The water-line is six or eight inches above the top row of 
tubes. The tube-plates below the water-line are sufficiently 
stayed by the tubes ; above the water-line the flat plates are 
stayed by through rods or stays as in Plate I, by diagonal 
stays like those shown by Fig. 63, page 159, or otherwise. A 
pair of cylindrical boilers in brick setting are shown by Figs. 
39 and 40, on pages 102 and 103, with the furnaces under 
the front (right-hand) end. The products of combustion pass 
back over a bridge-zvall, limiting the furnace, to the back end, 
then forward through the tubes and up the uptake to the flue 
which leads to the chimney. 

The shell commonly extends beyond the front tube-plate, 
as shown at the right in Fig.. 1, and is cut away to facilitate 
the arrangement of the uptake. The. boiler is usually sup- 
ported by cast-iron brackets riveted to the shell ; the front 
brackets may rest on or be fixed to the supporting side walls, 
but the rear brackets should be given some freedom to avoid 
unduly straining the boiler by expansion. Thus the rear 
brackets may rest on rollers, which in turn bear on a horizontal 
iron plate. The expansion takes place toward the back end of 
the boiler, and to allow for this expansion a space is left 
between the back tube-sheet, and the arch of fire-brick back 
of the boiler. 



TYPES OF BOILERS. 




STEAM-BOILERS. 




TYPES OF BOILERS. 5 

The boilers shown by Figs. 1 and 2 and by Plate I each have 
two steam-nozzles, one near each end. The safety-valve is 
usually attached to the front nozzle, which is above the fur- 
nace. The steam-pipe leading steam from the boiler is at- 
tached to the rear nozzle, which is over the back end of the 
boiler, where ebullition is less violent, and consequently there 
is less danger that water will be thrown into the steam-pipe. 

Boilers of this type commonly have a manhole on top nta* 
the middle, and a hand- hole near the bottom of each tube- 
sheet, as shown on Plate I, to give access to th? interior of 
the boiler and to facilitate washing out. Marp boilers are 
now made with a manhole near the bottom of the front tube- 
sheet, in addition to the one on top. All parts of the boiler 
can then be cleaned and inspected whenever desirable. Some 
of the lower tubes must be left out when there is a manhole 
in the tube-sheet, but this is of small consequence, as the 
lower tubes are not efficient, and enough heating-surface can 
be provided elsewhere. The. omission of the lower tubes re- 
quires also special stays for the portion of the tube-sheet left 
unsupported. 

The feed-pipe for the boiler shown by Plate I enters the 
front head at the left, below the water-line, and runs toward 
the back end of the boiler, where it may end in a perforated 
pipe leading across the boiler. The feed-pipe may enter the 
top of the boiler, near the back end, and terminate in a similar 
perforated transverse pipe below the water-line. 

A blow-off pipe leads from the bottom of the shell near the 
back tube-sheet. On the blow-off pipe there is a plug or valve 
which may be opened when steam is up, to blow out mud and 
soft scale that may collect in the boiler. The boiler is com- 
monly set with a slight inclination toward the rear so that 
mud may collect near the blow-off pipe. The boiler may be 
emptied by allowing the water to run out at the blow-off pipe. 

About half of the shell, two thirds of the back tube-sheet, 
and all the inside surface of the tubes come in contact with 



STEAM-BOILERS. 



the products of combustion and form the heating-surface ; all 
the heating-surface is below the water-line. 

The boiler-setting, shown by Figs. 39 and 40 on pages 
102 and 103 is made of brick laid in cement or mortar; all 
parts that are directly exposed to the fire are lined with fire- 
brick. The walls have confined air-spaces to reduce transmis- 
sion of heat. The boiler front is commonly made of cast iron, 
and has fire-doors leading to the furnace, and ash-pit doors 
opening from the ash-pit, or space below the grate ; there are 
also large doors giving access to the tubes through the 
smoke-box at the front end of the boiler. The furnace is 
formed by the side walls, the bridge, and the lower part of the 
boiler front, which latter is lined with fire-brick above the 
grate. Doors through the rear wall give access to the space 
back of the bridge. The top of the boiler is covered by a 
brick arch or by non-conducting material. 

Two-flue Boiler. — The cylindrical flue-boiler differs from 
the tubular boiler mainly in replacing the fire-tubes by one 
or more large flues. Fig. 3 shows such a boiler with two 




Fig. 3. 

flues. This type of boiler is usually longer than a tubular 
boiler, but even so it has less heating-surface and is less 
efficient in the use of coal. Nevertheless the greater sim- 
plicity and accessibility for cleaning recommend it where feed 
water is bad. 

The setting of a flue-boiler resembles that for the cylin- 



TYPES OF BOILERS. 



drical tubular-boiler. 




The figure shows two loops at the top 
of the shell for hanging the 
boiler; a crude method of sup- 
porting, suitable only for small 
and short boilers. 

Plain Cylindrical Boiler. — 
In places where fuel is very- 
cheap, especially where it is a 
waste product, as at sawmills, 
the plain cylindrical boiler is fre- 
quently used. Its external ap- 
pearance is similar to that of the 
two-flue boiler (Fig. 3), except 
that there are no flues and the 
ends are commonly hemispheri- 
cal or else curved to a radius 
equal to the diameter of the 
shell. Such plain cylindrical 
boilers are also employed to util- 
ize the waste gases from blast- 
furnaces. They are commonly 
30 to 42 inches in diameter and 
from 20 to 40 feet long. They 
have been made 70 feet long. 
With such extreme lengths spe- 
cial care must be taken to insure 
equal distribution of the weight 
to the supports and to provide 
for expansion. 

Lancashire Boiler. — This 
boiler, shown by Fig. 4, is a two- 
flue shell-boiler with furnaces 
in the tubes; it is therefore an 
internally-fired boiler, in which 
it differs from the two pre- 



8 STEAM-BOILERS. 

ceding types, which are externally-fired. The chief difficulty 
in the design of these boilers is to provide sufficiently large 
furnaces without making the external shell too large. As com- 
pared with the cylindrical tubular boiler, this boiler will be 
sure to have long, narrow grates, with a shallow ash-pit and a 
low furnace-crown : the boiler also appears to be deficient in 
heating-surface. In compensation, radiation and loss of heat 
from the furnace are almost entirely done away with, and the 
thick outside shell, with its riveted joints, is not exposed to 
the fire, as with the tubular boiler. The flues are made in 
short sections riveted together at the ends, thus forming a 
series of stiffening rings that add very much to the strength 
of the flues against collapsing. Conical through-tubes, ver- 
tical or inclined, give increased heating-surface, break up the 
currents of the hot gases, improve the circulation of the water, 
and strengthen the flues. These tubes are small enough at 
the lower end to pass through the hole cut in the flue for the 
upper end, and thus are readily put in or taken out for repairs. 

The flat plates at the ends of the shell are stayed by 
gusset-stays or triangular flat plates to the shell of the boiler. 
The boiler is provided with a manhole near the back end and 
a safety-valve near the front end. Steam is taken through a 
horizontal dry-pipe, perforated on the top. 

Galloway Boiler.— This boiler has two furnace-flues at the 
front end, like the Lancashire boiler. Beyond the furnace 
the two flues merge into one broad flue, having the upper and 
lower surfaces stayed by numerous conical through-tubes, like 
those shown in Fig. 4 for the Lancashire boiler. 

Cornish Boiler. — This boiler was developed in conjunction 
with the Cornish engine, and both boiler and engine long had 
a reputation for high efficiency. It differed from the Lanca- 
shire boiler in that it had but one flue ; it formerly did not 
have cross-tubes. The one furnace of the Cornish boiler, with 
a given diameter of shell, can have better proportions than 
the two furnaces of the Lancashire boiler, but there is even 



TYPES OF BOILERS. 



9 



greater difficulty to get sufficient grate-area and heating-sur- 
face- The high economy shown by these boilers when used 
with the Cornish pumping-engine was due to a slow rate of 
combustion, and to the skill and care of the attendant, who 
was usually both engineer and fireman, and who was stimu- 
lated by a system of competition and awards, maintained by 
the mine-owners in that district. 

The Lancashire and the Cornish boilers are set in brickwork 
which forms flues leading around the outside shell, thus mak- 
ing the shell act as heating-surface. Fig. 5 gives a cross-sec- 




Fig. 5. 



tion of the Lancashire boiler and its setting. After the gases 
from the fires leave the internal flues they are directed into 
the flue a and come forward ; then they are transferred to the 
flue b and pass backward ; finally they come forward in the 
flue c, and are then allowed to pass to the chimney. This 
forms what is known as a wheel-draught. In some cases the 
gases divide at the rear and come forward through both side 



TO STEAM-BOILERS. 

flues a and b, and uniting pass back through c and thence to 
the chimney, forming a split-draagJit. 

Vertical Boilers.— Boilers of this type have a cylindrical 
shell with a fire-box in the lower end, and with fire-tubes run- 
ning from the furnace to the top of the boiler. Large verti- 
cal boilers have a masonry foundation and a brick ash-pit; 
small vertical boilers have a cast-iron ash-pit that serves as 
foundation. Vertical boilers require little floor-space; if 
properly designed they give good economy, or they may be 
made light and powerful for their size, when economy is not 
important. 

Fig. 6 shows a large vertical boiler designed by Mr. 
Manning. It is made 20 to 30 feet high, so that there is a 
large heating-surface in the tubes. The shell is enlarged at 
the fire-box co provide a larger furnace and more area on the 
grate. The internal shell which forms the fire-box is joined 
to the external shell by a welded iron ring called the founda- 
tion-ring. This internal shell should be made of moderate 
thickness to avoid burning or wasting away under the action 
of the fire. Being under external pressure, the shell of the 
fire-box must be stayed to avoid collapsing. For this pur- 
pose it is tied to the outside shell at intervals of four or five 
inches each way, by bolts that are screwed through both 
shells and riveted over cold, on both ends. The stays near 
the bottom have each a hole drilled from the outside nearly 
through to the inside end. Should any stay break or become 
cracked, steam will escape and give warning to the fireman. 

The tubes are arranged in concentric circles, leaving a 
space about ten inches in diameter at the middle of the 
crown-sheet ; the corresponding space in the upper tube- 
sheet provides for the attachment of the nozzle for the steam 
outlet. 

There are numerous hand-holes in the shell outside of the 
fire-box, some near the crown-sheet, and some near tne foun- 
dation^ring, and these are the only provision for cleaning the 



TYPES OF BOILERS. 



II 



WATER LEVEL 




Fig. 6. 



12 



STEAM-BOILERS. 



boiler, which consequently is adapted for the use of good 
feed-water only. The feed-pipe enters the shell at one side 
and extends across the boiler; it is perforated to distribute 
the feed-water. 

The sides of the fire-box, the remaining surface of the 
tube-sheet allowing for the holes for the tubes, and the inside 




Fig. 7. 



of the tubes up to the water-line form the heating-surface : 
the inside of the tubes above the water-line form the super 



TYPES OF BOILERS. 



13 



heating-surface, since it transmits heat from the gases to the 
steam and superheats it. 

This type of boiler has found favor at factories where 
floor-space is valuable, since a powerful battery of boilers may 
be placed in a small fire-room. 

A small vertical boiler adapted for hoisting, pile-driving, 
and other light work is shown by Fig. 7. It commonly has 
a short smoke-pipe, into which the exhaust steam from the 
engine is turned to form a forced draught and give rapid 
combustion. Under this treatment the upper ends of the 
tubes frequently give trouble by leaking. To avoid this diffi- 
culty the tubes are sometimes ended in a sunken or submerged 
tube-sheet which is kept below the water-line, as shown by 
Fig. 8. The space between the edge of the tube-sheet 




Fig. 8. 



and the outside shell is likely to be contracted, and not to 
give proper exit for the steam formed on the tubes and 
crown-sheet. Furthermore, the cone forming the smoke- 
chamber above the tube-sheet is subjected to external pres- 
sure and is likely to be weak. 

A form of vertical boiler having a sunken tube-plate is 
shown by Fig. 9. It was at one time much used for steam 
fire-engines, but to save weight it was so crowded with tubes 



14 



STEAM-BOILERS. 



and the water-spaces were so contracted that it gave much 
trouble when forced, as at a fire. 

Fire-engine Boiler. — A boiler for a steam fire-engine 
should be light and compact, able to make steam quickly and 




Fig. 9. 

to steam freely when urged. They have small water-space 
and large heating-surface for their size, but are not economi- 
cal in the use of fuel. It is customary to use cannel-coal for 
fire-engines, as it burns freely without clogging. A forced 



TYPES OF BOILERS. 



15 



draught is obtained by exhausting steam up the smoke-pipe. 
When standing in the engine-house ready for duty the 
boilers are kept hot by connecting them to a heating- 
boiler in the basement. The connection is so made with 
snap-valves that it is broken by pulling the fire-engine out of 
position. 




000000000 ooooon n 00ooooo °oo 
0000000000 000000 T 0000000 

ilfli^.-.-.-.-.* . . . e uuoouo °ooooooooo 




Fig. 10. 



Scotch Boilers. — A single-ended three-furnace Scotch 
marine boiler is shown in perspective by Fig. 10; Fig. tt 
gives the working drawings of a similar boiler with two fur- 
naces. The arrangement of the furnaces in the flues, is simi- 
lar to that for the Lancashire boiler, shown, by Fig. 4. The 
furnace-flue leads into a combustion-chamber, from which 



1 6 STEAM-BOILERS. 

the products of combustion pass through fire-tubes to the 
uptake, which is bolted onto the front end of the boiler. 

The flues are from three and a half to four and a half 
feet in diameter; the size of the boiler depends on the 
number and size of the flues. Large boilers have as many 
as four flues. A three-furnace boiler commonly has three 
combustion-chambers, while a four-furnace boiler may have 
two, into each one of which two furnaces lead. Double- 
ended boilers have furnaces at each end, and resemble 
two single-ended boilers placed back to back. A double- 
ended boiler is lighter, cheaper, and occupies less space than 
two single-ended boilers. In the best practice there are 
two distinct sets of combustion-chambers for the two sets 
of furnaces. To still further lighten double-ended boilers, 
common combustion-chambers for corresponding furnaces at 
the two ends have been used. The results from such 
boilers have not been satisfactory, more especially when 
used under forced draught in the closed stoke-holes of war- 
ships ; there has been so much trouble from leaky tubes 
under such conditions that forced draught has been aban- 
doned in many cases, and ships have consequently failed to 
make the speed anticipated. 

The circulation of water is defective in all Scotch boilers, 
and more especially in double-ended boilers. Considerable 
time — three or four hours — is always allowed for raising steam. 
Frequently some arrangement is made for drawing cold water 
from the bottom of the boiler and returning it near the water- 
line, while steam is raised. Haste and lack of care are liable 
to cause leakage from unequal expansion. The flue has the 
highest temperature of any part of the boiler and consequently 
expands the most, so that some allowance for expansion must 
be made or it will strain the tube-sheets and cause leaks. The 
methods of providing for expansion and at the same time 
stiffening the flues against collapsing under external pressure 
are shown on pages 221 to 236, and will be described in de-' 
tail later on. 



TYPES OF BOILERS. 



*7 




i8 



STEAM-BOILERS. 



Locomotive-boilers. — The typical American locomotive- 
boiler is shown by Plate II. Fig. 12 gives a perspective view 
of a boiler of the locomotive type used for small factories, or 
where steam is required temporarily ; it has no permanent 
foundation, but is supported on brackets at the fire-box and 
by a pedestal-bearing on rollers near the back end. 

The. locomotive-boiler consists essentially of a rectangular 
fire-box and a cylindrical barrel through which numerous tubes 
pass from the fire-box to the smoke-box, which forms a con- 
tinuation of the barrel, and from which the products of com- 
bustion pass up the smoke-stack. 

The fire-box is joined to the outer shell at the bottom by 
a forged rectangular foundation-ring, similar (except in shape) 




Fig. 12. 



to the foundation-ring of a vertical boiler. Near this ring are 
several hand-holes for clearing out the space between the fire- 
box and the shell, commonly called the water-leg. The boiler 



TYPES OF BOILERS. 



19 



also has a manhole at the top of the barrel. The water-leg is 
staved by screwed stay-bolts riveted cold at the ends. 

The flat crown-sheet is stayed to a system of crown-bars 
which rest on the side sheets of the fire-box and are also slung 
from the shell. 

Plate III shows a locomotive -boiler with a flattened top over 
the fire-box to which the crown-sheet is stayed by through-bolts. 

The excessive compression brought to the sheets, forming 
the inner sides of the water-leg, by the crown-bars which get 
an end support at these sheets and the great depth required in the 
crown-bar in order to give the strength needed, have made it 
impracticable to use crown-bars on boilers carrying more than 
200 lbs. of steam-pressure. 

The method shown by Plate III is commonly adopted on 
large boilers of this class. The stay-bolt has a tapering head 
which is drawn into a tapering hole in the crown-sheet. This 
makes a tight joint and does not increase to any extent the amount 
of metal in contact with the crown-sheet. 

The whole matter of staying will be discussed more fully in 
the chapter on staying. 

The tubes for a locomotive-boiler are smaller than for a sta- 
tionary boiler and are spaced much more closely. Generally 
about 2-inch tubes are used in locomotives, although in some 
cases smaller tubes have been used. The tubes are spaced at 
the intersection of sets of parallel lines drawn at angles of 30 and 
150 with reference to a horizontal line. 

By this means a greater number of tubes can be gotten into 
a given space than could be done by spacing in vertical and 
horizontal rows, as is customary in horizontal multitubular boilers 
like Figs. 1 and 2 and Plate I. This is to obtain a large heating- 
surface required by the high rate of combustion, which often 
exceeds one hundred pounds of coal per square foot of grate- 
surface per hour. The boiler works under a strong forced 
draught, produced by throwing the exhaust up the smoke-stack. 

The boiler is fastened rigidly to the frame of the locomo- 



20 STEAM-BOILERS. 

tive at the smoke-box end; a small longitudinal motion on the 
frame at the fire-box end is provided by expansion- pads, shown 
by Fig. 4, Plate II. 

Locomotive Type of Boiler.— Reference has already been 
made in connection with Fig. 12 to a boiler of locomotive type 
used for stationary purposes. Plate IV shows a modification 
of the locomotive type designed by Mr. E. D. Leavitt to give 
high evaporative efficiency. The boiler represented has a barrel 
go inches in diameter, and it is 34 feet 4 inches long over all. 
The working pressure is 185 pounds. 

The fire-box of this boiler is spread at the bottom to give 
increased grate-area, and contains two separate furnaces, shown 
by the section A A on Plate IV. The products of combus- 
tion pass through openings, shown by section BB, into a com- 
bustion-chamber, which has the section shown at CC. From 
the combustion-chamber, the gases pass through tubes to the 
smoke-box and uptake. As far as the combustion-chamber 
the top of the boiler is flattened to facilitate the staying of the 
crown-sheets of the furnace, passages, and combustion-cham- 
ber; the barrel of the boiler beyond the combustion-chamber 
is cylindrical. 

The boiler is somewhat complicated in construction and 
staying, and must be handled with care, especially in starting, 
to avoid straining from unequal expansion. It is adapted for 
the use of good feed-water only. 

Boilers of the locomotive type were at one time used for 
torpedo-boats. The fire-box was made shallower than for 
locomotive-boilers, and forced draught in a closed stoke-hole 
was used, the rate of combustion being even higher than on 
locomotives. Whatever may have been the reasons, it was a 
fact that this type of boiler, which is very reliable on locomo- 
tives, gave much trouble in torpedo-boats. 

Water-Tube Boilers. — The boilers thus far considered 
have an external shell containing a large body of water. Heat 
is communicated to the water through the shells or through 



TYPES OF BOILERS. 21 

the sides of internal furnaces, and also by carrying the gases 
through tubes or flues. The boilers and water contained, are 
heavy and cumbersome, and the shells under high pressure 
must be made very thick. If the boiler fails either through 
some defect or through carelessness of attendants, a disastrous 
explosion is likely to take place. If properly designed and 
made and if cared for by competent and careful attendants 
they are safe, reliable, and durable. The large mass of hot 
water tends to keep a steady pressure, though at the expense 
of rapidity of raising steam or of meeting a sudden demand 
for more steam. 

A large number of water-tube boilers of all sorts of shapes 
and methods of construction has been devised to overcome 
the admitted defects of shell-boilers. They all have the 
larger part of their heating-surface made up of tubes of moder- 
ate size filled with water. They all have some form of separa- 
tors, drum, or reservoir in which the steam is separated from 
the water; some of these boilers have a shell of consider- 
able size, thus securing a store of hot water and a good free- 
water surface for disengagement of steam. Such shell, drum, 
or reservoir is either kept away from the fire or is reached 
only by gases that have already passed over the surface of 
water-tubes. 

The tubes are of moderate or small diameter, and so can 
be abundantly strong even when made of thin metal. Even 
if a tube fails through defect in manufacture or through wast- 
ing during service, it will not cause a true explosion ; and yet 
the failure of a tube in a confined boiler or fire-room has fre- 
quently caused death by scalding. 

Water-tube boilers may be made light, powerful, and 
compact, and are well adapted for use with forced draught. 
Steam may be raised rapidly from cold water, but pressure 
falls as rapidly if the fire loses intensity, and fluctuations in 
pressure are likely to occur. The two greatest difficulties are 
to secure a proper circulation of water through the tubes 



2 2 S"l EA M -BOILERS. 

and to properly separate the steam from the water. There 
are many joints that may give trouble by leaking, and some 
types have numerous hand-holes for cleaning the tubes, which 
may further increase the chances of petty leaks. 

A few water-tube boilers will be described as illustrations; 
many others equally good will be passed by, since it will be 
impossible to describe all. 

Babcock and Wilcox Boiler.— This boiler, which is 
shown by Figs. 13 and 14, is a water-tube boiler having one or 
two cylindrical drums at the top from either end of which are 
suspended "headers" into which the tubes running from end 
to end are expanded. 

The headers are made of steel castings or forgings, box-like 
in shape, with holes for tubes staggered so that the tubes taken 
as a whole are in horizontal rows, but not in vertical rows — an 
arrangement that gives a better spreading of the products of 
combustion among the tubes. 

Opposite the end of each tube there is a hand-hole, as shown. 
Each header is connected with the corresponding header at the 
opposite end by the tubes making a "section." The capacity of 
a boiler of this class is increased by increasing the number of 
tubes in a section and by increasing the number of sections con- 
nected to the drum or drums at the top: thus a boiler 12 wide 
and 9 high would have 12 sections and 9 tubes in each header. 
If there were a very strong draught it might be advisable to have 
more tubes in a header. 

A double-deck boiler is one where a second header is joined 
to the end of the first header. The two headers are joined by 
a piece of tube which is expanded into each. Two headers, 
each 9 high, when joined in this way make 18 high. 

By means of a special tile made to fit between the tubes the 
gases are obliged to circulate, as shown by the arrows. 

The gases escape out of the back wall. In some cases where 
there is not much room the gases have been brought up between 
the drums at the back end, thus enabling the back wall to be 



TYPES OF BOILERS. 



23 




24 STEAM-BOILERS. 

against the wall of the building. The lower half of the cylin- 
drical shell serves as heating-surface, but it is at such a height 
above the fire and is so shielded by the water-tubes that it is not 
liable to be overheated. The boiler is hung from cross-girders 
front and back, whieh in turn are supported on iron columns, 
and the brick setting is only a screen to retain the heat. 

The circulation of the water in the boiler is down from the 
shell at the rear to the water-tubes, forward and upward through 
flhe tubes, in which course it is partially vaporized and conse- 
quently has a less average density, then up into the shell at 
the front, where the steam and water separate; the water in the 
shell flows continually from the front to the rear to supply the 
current through the tubes. 

Beneath the back headers there is a mud-drum into which 
scale settles. The blow-off pipe leads from this mud-drum out 
through the setting. 

Heine Boiler. — This boiler, shown by Fig. 15, consists of 
one or two drums, depending on the size of the boiler, with a rec- 
tangular box-like water-leg connected at each end. 

These legs are built out of plate and riveted to the drum or 
drums. 

Tubes run from leg to leg. Opposite the end of each tube 
there is a hand-hole through which the tube may be expanded 
or cleaned from scale. The boiler is set with the back end com 
siderably lower than the front end, as shown by the cut. 

The gases are made to circulate, as indicated by the arrows. 

The feed-water is taken into a small drum inside the main 
drum. It becomes heated here and deposits some of the lime 
salts, which are generally found in feed-water. These deposits 
are blown out from time to time through the pipe shown. A 
similar blow-off connection is shown at the bottom of the back 
water-leg. 

The water circulation is from the front towards the back in 
the drum and from the back towards the front in the tubes. 

A mixture of steam and water rushes out of the tubes at the 



TYPES OF BOILERS. 



25 



front end and up into the drum where it strikes against a deflect- 
ing plate placed so as to keep water from being sprayed into the 
steam space. 

A similar plate is to be found in the drum of the Babcock 
and Wilcox boiler. The velocity into the drum is greater in the 
Babcock and Wilcox than in the Heine. 

The water-legs of the Heine boiler are stayed by hollow stays 




Fig. 15. 

expanded or screwed into the two plates at points located between 
the tubes. 

The Stirling Boiler. — This boiler, shown by Fig. 16, has 
three cylindrical drums at the top and a larger drum at the 
bottom, connected by tubes having a slight curvature at the 
ends. The two forward drums at the top have also a connec- 
tion below the water-line through pipes not indicated. All 
three upper drums have their steam-spaces connected by 
piping. The water-line is indicated by a dotted line. 



26 



STEAM-BOILERS. 



The feed-water is introduced into the rear upper drum, 
from which it passes down through the rear system of pipes, 
which act mainly as a feed water heater, and enter the lower 
drum, where the water deposits any lime compound that it 
may contain, from whence it may be blown out at intervals. 
Fire-brick bridges cause the products of combustion to pass 
in succession through the three systems of water- tubes as 
shown by the arrows. 




Fig. i 6. 



The circulation through the tubes is very rapid and the tubes 
being nearly vertical do not collect much scale. 

These two facts have made this boiler work satisfactorily 



TYPES OF BOILERS. 



2 7 



with bad feed-water when some other types of boiler would not 
answer at all. 

The water-level is not the same in all three drums when the 
boiler is working. The front drum will show a level 6 inches 
higher than the rear drum if the boiler is forced hard. 

Water Tube Marine Boilers. — With the advent of very 
high steam pressures on steamships there has been a tendency 
to replace the Scotch boiler by some form of water-tube boiler. 

The objects that are sought in water-tube boilers for steam- 
ships are a larger power for the weight and the ability to carry 
high pressures. 

It is still a question whether the water-tube boiler will or 
can replace the Scotch boiler. 




Fig. 17. 

Babcock and Wilcox Marine Type. — This boiler, shown 
by Fig. 17, is made up of sections connected at one end to the 



2 8 STEAM-BOILERS. 

bottom of a drum running at right angles to the tubes, and at the 
other end to a tube leading into the side of the drum at the level 
of the water-line. The side sections are continued down to the 
level of the grate, the tubes being replaced by forged steel boxes 
of 6-inch square sections at the furnace sides. These boxes are 
located one above the other on the same angle as the tubes; they 
take the place of brickwork, insure a cool side casing, and prevent 
the adherence of clinkers. 

Placed across the bottoms of the front header ends and con- 
nected with them by 4-inch tubes is a forged steel box of 6-inch 
square section. 

This box is situated at the lowest corner of the bank of tubes 
and forms a blow-off connection or mud-drum, through which 
the boiler may be completely drained. 

The circulation of water in the tubes is from the front to the 
back, where the connecting-tube leading from each section to 
the drum discharges a mixture of steam and water against the 
baffle in the large drum. 

The path of the gases is shown by the arrows. 

The Belleville Boiler is represented by Fig. 18; it con- 
sists essentially of a series of coils of pipe made up with bends 
and elbows around which the products of combustion pass 
on the way to the chimney. At the top there is a steam-drum 
A, connected by two circulating-pipes B and C, with a drum 
D at the bottom. From the mud-drum D a rectangular feed- 
supply runs across the front of the boiler to all the coils or 
elements of the boiler. Each element is continuous from the 
feed-supply to the steam-drum, and is made up of slightly 
inclined pieces of pipe with horizontal bends or connections 
at the end. The effect is much as though a helical coil were 
flattened into two vertical tiers of pipes. The amount of 
water in the boiler is so small that it cannot be run without 
an automatic feed-water regulator, which in turn requires trie 
attention of an expert feed-water tender. The several ele- 
ments deliver a mixture of water and steam to the steam- 



TYPES OF BOILERS. 



29 



-^K^S 








o 



e> 












in 



m 



B 



E 




3o 



STEAM-BOILERS. 



drum, which does not appear to act efficiently as a separator, 
as an external separator is placed between the boiler and the 
engine. The feed-water is supplied to the steam-drum and 
passes through the external circulating-pipes to the mud-drum, 
where it deposits much of its impurities. 

Thornycroft Boiler. — The boiler represented by Figs. 19 
and 20 was built for the torpedo-boat destroyer, "Daring," 
by Mr. Thornycroft; boilers of slightly different forms have 
been fitted by him, in torpedo-boats and steam-launches. 

The boiler consists essentially of a large drum or separator 
at the top and three drums at the bottom, connected by a large 
number of bent-tubes. There is, inside of the casing, a large 
tube connecting the top drum to the middle drum at the bottom, 
and this drum is connected to the side drums by smaller pipes. 
The circulation is down from the top drum to the middle lower 
drum, and from that to the side drums, then up through all the 
bent water-tubes to the upper drum, where mingled water and 
steam is delivered against a baffle-plate above the water-line. 
Steam is drawn from a nozzle at the front end of the top 
drum. 

The arrangement of grates and -fire-doors is shown in 
elevation and section by Fig. 19. The middle drum divides 
the grate into two parts; over that drum is a space which is 
in communication with the uptake, as shown by Fig. 20. 
The products of combustion pass among the tubes leading 
from the middle drum; the tubes to the outer drums intercept 
the radiant heat which would otherwise strike on the boiler- 
casing. 

The boiler-setting is an iron frame, and the casing is thin 
plate iron lined with incombustible non-conducting material. 
There are numerous doors through the casing for cleaning the 
tubes. 

This boiler has proved very successful with a forced 
draught, making steam freely and giving little trouble. The 
boiler contains so small an amount of water that steam may 



TV PES OF BOILERS. 



31 





3 2 



STEAM-BOILERS 



be raised quickly, and any demand for steam can be quickly 
met. On the other hand, the feed-supply must be regulated 
with care and skill, and the pressure is liable to fluctuate. 




Fig. 2i. 



The Yarrow Boiler. — The form of boiler used by Mr. 
Yarrow for torpedo-boats, is shown by Fig. 21. It resem- 
bles in general arrangement a form used by Mr. Thorny- 



TYPES OF BOILERS • 7>3 

croft with one grate. It, however, differs radically in certain 
particulars, namely, in that the tubes are straight and that 
they enter the upper drum below the water-line, and in that 
there ars no pipes outside the casing to carry water from the 
jpper drum to the lower drum or reservoirs. Some of the 
tubes deliver water and steam to the upper drum, from which 
steam is drawn ; other tubes carry water from the upper 
drum to the lower drums. A given tube may act sometimes 
in one way and sometimes in the other. Naturally those 
tubes which receive the most heat and make the most steam 
deliver to the upper drum, and tubes that receive less heat 
carry down water. 

The air for the fire is drawn from an iron box or casing 
outside the boiler-casing, so that the heat escaping from the 
boiler-casing is largely carried back to the fire, and the fire- 
room, and also the rest of the vessel, is heated up less. 

The Almy Boiler. — This boiler, which is represented by 
Fig. 22, is made of short lengths of pipe screwed into return- 
bends and into twin unions. At the bottom is a large tube or 
pipe forming three sides of a square at the sides and back of 
the grate. From this water-space the tubes lead into a similar 
structure at the top. The steam and water are discharged into 
a separator in front of the boiler, from which steam is drawn; 
while the water separated therefrom, together with the feed- 
water, passes down through circulating -pipes to the bottom of 
the boiler. 

The boiler is provided with a coil feed-water heater above 
the main boiler. It is enclosed by a casing lined with non- 
conducting material. It is intended for general marine work. 

General Discussion. — In deciding on the type of boiler to 
be selected for any particular case there are a number of things 
to be considered. The following are the most important: 
i. The pressure to be carried. 
2. The quality of the feed-water. 



34 



STEAM-BOILERS. 



3. The variation in load. 

4. The size of the battery. 

5. The amount of land available. 

6. The cost of land. 

7. The fuel to be used. 

In general, it may be said that the more simple the boiler is,, 
the better it is; that all parts of the boiler should be easily 




Fig. 22. 



accessible, and that the boiler should be so designed that it will 
not strain itself by unequal expansion. 

The thickness of the steel needed in the shell of a boiler must 
increase as the pressure increases, and also as the diameter 
increases, as will be shown later. It is not considered advisable 



TYPES OF BOILERS. 35 

to transmit heat through plates over one half an inch in thick- 
ness. 

For high pressures this means that if shell boilers, like Figs. 1 
and 2, are to be used the diameter must not be greater than 
60 or 66 inches, thus limiting the horse-power of a single unit 
to from 80 to 125 boiler horse-power, depending on the kind of 
coal used and the rate of combustion. 

This type of boiler is the least expensive, and if there were 
ample room and if the land occupied were inexpensive, it might 
be advisable to instal a large number of these small units to 
make up the horse-power desired. If, however, land were ex- 
pensive, or if there were but a small amount of land available, 
then this type could not be considered. 

A vertical boiler, like the Manning, or some form of water- 
tube boiler, like the Babcock and Wilcox, the Heine, or the 
Stirling, would probably be selected. 

If the cost of land were extremely high water-tube boilers 
might be located on the second, third, and fourth floors of a build- 
ing and discharge steam into a common main supplying engines 
in the basement. This arrangement is common in power- and 
lighting-stations located in the middle of a city. 

There is no difficulty in making a building sufficiently strong 
to carry the weights. 

There should be a sufficient number of boilers in the battery, 
so that one could be shut down and the others carry the load. 
As a boiler can be run from 25 to 30 per cent over its rated 
capacity this means that there should be at least four boilers 
in the battery if the plant is to run continuously. It is not cus- 
tomary to install units of more than 350 or 500 horse-power even 
in the largest batteries. 

The quality of the feed-water must also be considered in 
deciding how many boilers there are to be in the battery. If 
the feed-water Is very bad it may be necessary at times to have 
two boilers shut off from the line. More boilers are needed when 
the feed-water is of poor quality, not only for the reason mentioned, 



36 STEAM-BOILERS. 

but also because of the poorer efficiency of the heating-surface 
due to deposits of scale. 

The heating value of the fuel also enters as a factor in deter- 
mining the number of boilers needed. 

If a steady pressure is to be maintained with as little fluctua- 
tion as possible, a boiler with a large water-space should be 
chosen. Such a boiler will meet a sudden demand for steam 
without much drop in pressure; on the other hand, it takes a 
long time to increase the pressure. 

The Scotch boiler and a modification of the same having the 
combustion-chamber in a space bricked in at the end of the 
boiler have been used successfully for the operation of draw- 
bridges, where the demand for steam is at the rate of 100 boiler 
horse-power for a period of from five to eight minutes two or 
three times an hour. 

The cost of boilers varies with the price of steel. At the 
present time, 1908, horizontal multitubular boilers cost, when 
set, about $11.50 per horse-power for boilers 60 to 66 inches in 
diameter. 

Water-tube bcilers about 200 horse-power per unit cost from 
$15.50 to $16.50 per horse-power, set ready to connect to the 
steam-main. 

Scotch boilers cost about $16.50 p?r horse-power in sizes 
ranging from 100 to 150 horse-power. 

Tables giving the diameters, ratings, width, length > and 
heights of settings of many of the common types of boilers have 
been added to the appendix. 

We believe that these tables will be useful to any one who 
may be making the preliminary design of a boiler plant. 



CHAPTER IT. 

SUPERHEATERS. 

Steam may be dry and saturated, primed or superheated. 

Dry and saturated steam and primed or "wet" steam, as it 
is sometimes called, at the same pressure have the same tem- 
perature. 

As bubbles of steam break through the surface of the water 
in a boiler some water is atomized into the steam- space where it 
floats just as moisture floats in the air. 

The amount by weight of such water floating in a total weight 
of one pound is called the priming. This priming is in certain 
types of boilers between .005 and .03. 

If heat is now added to the wet steam in the steam-space 
the water floating in the steam will vaporize and at the instant 
when all of this water has vaporized we have dry and saturated 
steam. If more heat is added the temperature of the steam will 
go up and the steam will become superheated; the amount of 
superheating in degrees being the difference between the tem- 
perature of the steam as observed and that of saturated steam 
of the same pressure. 

The specific heat of superheated steam is the amount of heat 
necessary to raise the temperature of one pound of superheated 
steam i° Fahrenheit. 

The specific heat has been found to increase with the pressure 
of the steam, and at any constant pressure to decrease as the 
number of degrees of superheating increases. 

37 



STEAM-BOILERS. 



The following table from the experiments of Thomas and 
Short gives the mean value of the specific heat for different 
pressures and different degrees of superheat. 



SPECIFIC HEAT OF SUPERHEATED STEAM. 









Pressure Lbs. 


Sq. In. 


Absolute. 






















Superheat. 


















6 


15 


3° 


50 


IOO 


200 


300 


20° 


-536 


•547 


.558 


571 


•593 


.621 


.649 


5° 


.522 


o3 2 


•542 


555 


-575 


.600 


.621 


IOO 


•5°3 


.512- 


.524 


537 


-557 


.581 


•599 


150 


.486 


.496 


.508 


522 


-544 


.567 


.585 


200 


-471 


.480 


.494 


5°9 


•533 


.556 


•574 


250 


.456 


.466 


.481 


496 


.522 


.546 


• 564 


300 


.442 


•453 


.468 


484 


"-S" 


•537 


•554 



Attached Superheater. — There are two classes of super- 
heaters, the attached and the independently fired. 

The attached is connected to the boiler, receives its heat from 
the fire under the boiler, and in general does not give more than 
150 degrees of superheat. 

Nearly all of the attached superheaters are connected to the 
steam and to the water-space of the boiler in such a way that 
they can be flooded while steam is being gotten up in the boiler. 

Some makes of attached superheaters may be flooded and 
the heating-surface used as additional steam-generating surface 
when the boiler is delivering saturated steam. 

Babcock and Wilcox Attached Superheater.— This 
superheater is shown by Fig. 23. It is located directly under 
the drums between the first and second gas passages. It is made 
of bent tubes expanded into steel headers, as shown. 

Steam is taken from the dry pipe in the top of each drum 
into the center of the top headers, and after passing through the 
tubes leaves at the outer end of the bottom header. From the 



SUPERHEATERS. 



39 



end of the bottom header a pipe leads up to a nozzle fastened to 
the drum of the boiler, but not connecting with the drum. In 
some instances these superheaters have been arranged to work 




Fig. 23. 



flooded with water when the boiler was not delivering superheated 
steam. 

Heine Attached Superheater.— Fig. 24 and the two 

cross-sections shown on the same cut gives the arrangement of 
the Heine superheater. 

The greater part of the products of combustion is made to 
circulate, as shown by the dotted arrows, and is utilized in generat- 
ing steam. 

A small part of the products of combustion is made to follow 
the path shown by the full arrows, and pass through the super- 
heater. The path of these gases will be made clear by the sec- 
tions BB and A A. 

Stirling Attached Superheater.— The attached super- 
heater is shown as the middle bank of small tubes in Fig. 25. 
The detail of this superheater is shown by Fig. 26, which is a 
cross-section taken through Fig. 25. 



4o 



STEAM-BOILERS. 




.1 ■ ■ 'I 



HMJ-lMJ-lJ-{#^ 





SUPERHEATERS. 



41 



Saturated steam from the front and rear drums enters the left- 
hand section of the upper drum (Fig. 26) through the holes shown 
near the top. This steam circulates through the tubes to and 




Fig. 25, 



from the lower drum, as shown by the arrows, and is drawn off 
at the right-hand end of the upper drum. 

There is a removable diaphragm in the lower drum and covers 
in the two diaphragms in the upper drum. These are provided 



42 



STEAM-BOILERS. 



so as to make it possible for a man to get at the ends of any tubes 
which may need to be re-expanded. 

When using saturated steam the two by-pass valves in the 
diaphragms in the upper drum are opened and the lower drum 




Fig. 26. 

is connected with the bottom of one of the other drums through 
valves and piping provided for flooding. 

Independently -fired Superheater.— The independently- 
fired superheaters are intended to give higher temperatures to 
the steam than can be obtained by an attached superheater. 



SUPERHEATERS. 



43 



Superheaters of this class give a thermal efficiency of about 
60 per cent. Different makers use different amounts of heating- 
surface for the same capacity and the same degrees of superheat- 
ing. It seems that about 3 square feet are needed per boiler 
horse-power if the steam is to leave at about 6oo° F. and was not 
primed more than one per cent on entrance to the superheater. 

In order to keep the temperature of the superheated steam as 
uniform as possible it is customary to make use of a Dutch oven 
furnace, a furnace with a fire-brick arch over the grate. This 
arch, by giving up heat at one time and by absorbing heat at 
another time, tends to keep the gases more nearly at a uniform 
temperature. 

Foster Independently -fired Superheater. — This is 
shown in longitudinal view by Fig. 27. Fig. 28 gives a section 




Fig. 27. 



through a tube and header and shows the cast-iron rings put on 
to give additional surface for absorbing heat, and also to prevent 
any rapid fluctuations in the temperature of the fire affecting the 
temperature of the steam. 



44 



STEAM-BOILERS. 



The inner tube shown in this cut is sometimes closed together 
at the ends but not tightly sealed. This tube, which is held in 
place by distance pieces in the shape of rivet- heads, causes the 



AAAAAr: 




steam to flow rapidly through the annular space between it and 
the outer tube. 

The steam enters Fig. 27 at the top and leaves at the bottom. 

American Independently-fired Superheater. — The 
American superheater is shown by Fig. 29. Like the preceding 
it is built with a Dutch oven-furnace. 

A "tempering" door located in the bridge-wall may also be 
used for regulating the temperature of the gases. 

The superheater is made up of headers, which are steel cast- 
ings joined together by steel tubes. The tubes from the bottom 
of one header enter the top of the header opposite. The steam 
circulates as many times as there are headers in one row and 
passes out at the bottom. 

The bottom tubes are of Shelby drawn nickel-steel and in 
some cases are covered with tile or cast iron. 

The headers are supported one on top of another with steel 
balls in between. These balls provide for the expansion of the 
tubes. 



SUPERI1EA TERS. 



45 




i 



46 STEAM-BOILERS. 

A superheater of this make, installed at the Massachusetts 
Institute of Technology, designed to superheat io ; ooo pounds 
of steam an hour at 250 pounds pressure with one per cent prim- 
ing, 250 F., had a grate-area of 15.6 square feet and 5583 square 
feet of heating-surface. 

Steam Pipe-fittings for Superheated Steam. — Steel 
castings are probably the best fittings to use on pipe lines carry- 
ing highly superheated steam. Steel fittings are expensive and 
are not to be found in stock. 

There is evidence tending to show that cast iron, especially 
if of a poor grade, is affected in its strength by superheated steam; 
there is no evidence, however, showing that gun-iron fittings 
have deteriorated under the action of superheated steam. 

Fittings on superheated steam lines are subjected to greater 
strains on account of the larger amount of expansion of the 
pipe and on account of the greater changes in temperature. 

Composition loses its strength at high temperatures and is 
unsafe to use with superheated steam. 



CHAPTER III. 
FUELS AND COMBUSTION. 

THE fuels used for making steam are coal, coke, wood, 
charcoal, peat, mineral oil, and natural and artificial gas. 
Various waste and refuse products, such as straw, sawdust, 
and bagasse, are burned to make steam. 

All coals appear to be derived from vegetable origin, and 
they owe their differences to the varying conditions under 
which they were formed or to the geological changes which 
they have undergone. 

Anthracite Coal consists almost entirely of carbon and 
inorganic matters; it contains little if any hydrocarbon. 
Some varieties, for example certain coals found in Rhode 
Island, appear to approach graphite in their characteristics, 
and are burned with difficulty unless mixed with other coals. 
Good anthracite is hard, compact, and lustrous, and gives a 
vitreous fracture when broken. . It burns with very little 
flame unless it is moist, and gives a very intense fire, free 
from smoke. Even when carefully used, it is liable to break 
up under the influence of the high temperature of the furnace 
when freshly fired, and the fine pieces may be lost with the 
ash. 

Semi-anthracite or Semi-bituminous Coal is intermedi- 
ate in its properties between anthracite coal and bituminous 
coal; it contains some hydrocarbon, is less dense than anthra- 
cite, it breaks with a lamellar fracture, and it burns readily 
with a short flame. 

47 



48 STEAM-BOILERS. 

Bituminous Coals contain a large and varying per cent 
of hydrocarbons or bituminous matter. Their physical prop- 
erties and behavior when burning, vary widely and with all 
intermediate gradations represented, so that classification is 
difficult. Three kinds may, however, be distinguished, as 
follows : 

Dry bituminous coals, which burn freely and with little 
smoke and without caking. 

Caking bituminous coals, which swell up, become pasty, 
and cake together in burning. They are advantageously used 
for gas-making. 

Long-flaming bituminous coals, which have a strong ten- 
dency to produce smoke ; some do and some do not cake 
while burning. 

Coke is made from bituminous and semi-bituminous coal 
by driving off the hydrocarbons by heat. Coke made as a 
by-product in gas retorts, is weak and friable, and has little 
value for making steam. Coke made in coking ovens, by 
partial combustion of the coal which is coked, is of a dark- 
gray color, porous, hard, and brittle. It has a metallic lustre, 
and gives out a slight ringing sound when struck. Sulphur 
in the coal may be burned out in coking, if the coal is moist 
or if steam is supplied during coking, so that coke may be 
comparatively free from this noxious element even when made 
from a poor coal. Coke burns without flame and makes a 
fierce fire when forced. 

Lignite, or brown coal, is of more recent geological 
formation than coal, and is in a manner intermediate between 
coal and peat. It frequently contains much moisture and 
mineral matter. It is used where good coal is difficult to get, 
and while the better varieties form a useful fuel, the poorer 
qualities have little value. 

Peat, or turf, is obtained from bogs. It consists of 
slightly decayed roots of the swamp vegetation mingled with 
more or less earthy matter. For domestic use it is cut and 



FUELS AND COMBUSTION. 49 

dried in the air. It is little used for making steam, though 
when pulverized, dried, and compressed it makes a useful 
artificial fuel. . 

Wood is used for making steam either in remote places 
where coal is hard to get and timber is plenty, or where saw- 
dust or other refuse wood is produced in quantity in manufac- 
turing operations. Wood is also used for kindling coal-fires. 
One cord of hard wood is equivalent to one ton of anthracite 
coal; one cord of yellow-pine is equal to half a ton of coal; 
other soft woods are, as a rule, of less value for fuel. 

Charcoal is made by charring wood ; it is but little used 
for making steam. 

Mineral Oil, in the form of crude petroleum or the refuse 
heavy oil left from the distillation of petroleum, is used for 
making steam, especially in the neighborhood of the Black 
Sea oil-field, and by steamers carrying oil from those fields. 
It is customary to throw the oil into the furnace in the form 
of finely divided spray through special spraying apparatus 
worked either with compressed air or with superheated steam. 
The use of superheated steam has its convenience only to 
recommend it, for it adds to the inert material to be uselessly 
heated. Special precautions must be taken, when petroleum 
is burned, to avoid flooding the furnace with oil and to pre- 
vent explosions of the vapor and burning of the oil in tanks 
or receptacles. 

Gases. — Natural gas from gas-wells has been used for 
making steam, usually in a crude and wasteful way. Some 
attempts have been made to use gas made from poor and 
smoky coal, in producer-furnaces like those used in metallurgi- 
cal operations; but the gain to-be expected is only the sup- 
pression of the smoke nuisance, which is rather a social than 
an economical problem. 

Artificial Fuels. — The small waste from coals and char- 
coals, sawdust, and other fine combustible material which 
cannot be sold in such shape, is sometimes made into cakes or 



5° 



S TEA M-BOILERS. 



briquettes by mixing it with some adhesive material and then 
compressing it. The adhesive materials have been wood-tar, 
coal-tar, or else clay. Tar is available in limited quantities 
only, and clay is disadvantageous since it adds to the inert 
material, of which fine fuel is liable to have an excess. 
Artificial fuels have some advantages for special purposes, and 
can be stored compactly ; they are used mostly where good 
fuel is difficult to get. 

Composition of Fuels. — The composition of a number 
of American coals, together with the total heat of combustion 
by William's bomb, is given in the table on page 51, which 
has been kindly furnished by Mr. Henry J. Williams. These 
results are a part of a very extended investigation by Mr. 
Williams, to be published in full in the near future. Most 
of the results are the averages of several separate analyses, and 
all may be depended upon to give a fair representation of the 
coals named. 

Analyses by Mahler of various European coals and of a 
few American coals, together with the total heat of combus- 
tion, are given in the table on page 52. 

The following table gives the composition of several rep- 
resentative petroleums : 

COMPOSITION OF PETROLEUMS. 



Pennsylvania, crude 

Caucasian, light. . . . 

heavy . . 

Petroleum refuse. . . 



Carbon. 


Hydrogen. 


Oxygen. 


84.9 


13-7 


1.4 


86.3 


13.6 


O.I 


86.6 


12.3 


I.I 


87.1 


11. 7 


I .2 



Specific 
Gravity. 



O.886 
O.884 
O.938 
O.938 



Heat of Combustion. — The number of thermal units de- 
veloped by the complete combustion of one unit of weight of 
a fuel is called the heat of combustion. It can be determined 
by burning the fuel in a properly constructed calorimeter. 
The most recent and best results are those obtained by the 
use of Mahler's bomb-calorimeter. This is a strong recep- 



FUELS AND COMBUSTION. 



51 







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FUELS AND COMBUSTION. 



53 



tacle of wrought iron or bronze, gold-plated or enamelled 
inside. The fuel to be tested is placed in a small platinum 
crucible, with an arrangement for igniting by electricity. 
The bomb is then filled with oxygen under the pressure 
of about twenty-five atmospheres, and is placed in a calo- 
rimeter-can containing water. There is oxygen in excess, so 
that the charge when ignited is completely consumed, and 
the resultant total heat of combustion is absorbed by the 
metal of the bomb and by the water in the calorimeter. The 
corrections for the calorimeter are determined by burning in 
it, some substance like naphthaline, for which the heat of com- 
bustion is known. The processes of making combustion 
determinations are simple and direct ; the difficulties are those 
incident to accurate measurements of temperatures, for which 
purpose the best physical thermometers are required. The 
experimenter must be an expert physicist, who has had expe- 
rience in the use of the apparatus. The table of composi- 
tion of fuels by Mahler * gives also the total heats of the 
fuels, determined by the same experimenter by aid of the 
bomb-calorimeter. 

An engineering expert who has had adequate training in 
a physical laboratory, may learn how to make determinations 
of the total heat of combustion ; an engineer in general prac- 
tice will find it advantageous to refer such work to an expert 
physicist. It is not too much to say that all crude forms of 
apparatus for finding total heat of combustion of fuels are 
useless and misleading. 

The heats of combustion of carbon in various forms as de- 
termined by Berthelot f are : 

Diamond 7859 calories. 

Diamond bort 7860.9 " 

Graphite 7901.2 " 

Amorphous from wood 8137.4 " 

* Bulletin de la Soc. d'Encouragement pour Industrie nationale, 1891. 
•r Comptes rendu, 1889. 



54 S 1 'EA M-B01L ERS. 

The heat of combustion of carbon in fuels may be taken at 
8140 calories, a calorie being defined as the heat required 
to raise one kilogram of water from I5°C to 16 C. This 
will give in the English system of units 14650 British thermal 
units, the B. T. U. being defined as the heat required to raise 
the temperature of a pound of water from 62 F. to 63 F. 
These definitions are founded on Rowland's determination of 
the mechanic equivalent of heat ; the difference between them 
and others commonly given are not of practical importance 
in this connection. 

The following table gives the heat of combustion of some 
elements and simple gases: 

Carbon burned to C0 2 8, 140 calories ; 14,650 B. T. U. 

Carbon burned to CO 4,400 

Hydrogen 34, 500 " 62,100 

Sulphur , 4,032 

Marsh-gas, CH 4 23,513 

Olefiant gas, C 2 H 4 2 1 , 343 

Carbon monoxide , . 4, 393 

Chemistry of Combustion. — Calculations concerning the 
heat of combustion of fuels and the amount of air needed for 
combustion, require a knowledge of the elements of chemistry. 

Elementary chemical substances are those that have not 
been decomposed, such as oxygen, hydrogen, and nitrogen. 
The elements enter into chemical combination in fixed propor- 
tions by weight ; these proportions are called the combining 
weights or the atomic weights of the elements. In the following 
table are given the most important chemical elements of fuels, 
their chemical symbols, and their atomic weights. The table 
gives other useful information which will be referred to later. 

A chemical combination, such as water, is represented by 
a formula consisting of the symbols of the elements entering 
into the combination, each symbol having a subscript which 
shows the number of times the combining or atomic weight of 



FUELS AND COMBUSTION. 



55 



iSymbol or 
| Composi- 
tion. 



Carbon 

Hydrogen 

Oxygen 

Nitrogen 

Sulphur 

Carbon d;oxide . . 
Carbon monoxide. 

Water 

Air 

Ash 



C 
H 
O 

N 
S 

co 2 

CO 

H,0 



Atomic or 

Molecular 

Weight. 



12 

I 
16 

14 
32 

12 4- 2 X l6 
12 -j- 16 
2 4- 16 



Specific 
Volumes. 





178 


20 


II 


21 


12 


74 


8 


10 


12 


81 


12 


39 



Specific 

Heat in 

Gaseous 

Condition 



3-409 

0.2175 

O.2438 

O.2169 
0.2450 
0.48* 

O.2375 
0.2f 



Density or 

Weight of 

One Cubic 

Foot. 



0.00551 
0.08928 
0.07837 

0.12345 
0.07806 

0.08071 



* Superheated steam. f Solid condition. 

the element occurs in the combination. This water is repre- 
sented by 

H,0, 

which indicates that water is made up of two portions of hy- 
drogen and one portion of oxygen. It is commonly said that 
two atoms of hydrogen and one atom of oxygen unite to form 
one molecule of water. As the atomic weight of hydrogen is I 
and the atomic weight of oxygen is 16, we have water formed 
of two. pounds of hydrogen to 16 pounds of oxygen. 

Again, carbon may unite with one portion of oxygen to 
form carbon monoxide or carbonic oxide, represented by CO ; 
or carbon may unite with two portions of oxygen to form 
carbon dioxide or carbonic acid, represented by C0 2 . Re- 
ferring to the table on page 54, it appears that the complete 
combustion to C0 2 gives more than three times the heat ob- 
tained from incomplete combustion to CO. But the resulting 
gas, CO may be burned with one more portion of oxygen, and 
will finally form CO a . Assuming that the double process will 
yield the same amount of heat per pound of coal as is ob- 
tained by direct combustion to C0 2 , we may calculate the 
heat of combustion of one pound of carbon monoxide as fol- 
lows : 



56 S TE A M -BOILERS. 

In the combustion of carbon to CO, 12 pounds of carbon 
unite with 16 pounds of oxygen, forming 28 pounds of CO, 
hence one pound of carbon will form 

12 + l6 = 2i lbs. of CO. 



The heat developed by burning these 2\ pounds of carbon 
monoxide, under our assumption, is 

14650 — 4400 = 10250 B. T. U., 

so that each pound of carbon monoxide will yield 

10250-^21 = 4393 B. T. U., 

as given in the table on page 54. 

The complete combustion in either case will give 

12 + 2 X 16 * 
V2 3t 

pounds of carbon dioxide for each pound of carbon. 

Calculation of Heat of Combustion.— If a fuel were a 
mechanical mixture of two chemical elements such as carbon 
and sulphur, the heat of combustion could obviously be found 
by calculating the parts separately and adding the results. For 
example, a mixture of 60 per cent carbon and 40 per cent 
sulphur would give 

0.60 X 14650 = 8790.0 
0.40 X 4032 = 1612.8 

10402.8 B. T. U. 

for each pound of the mixture. 

Fuels, as a rule, contain carbon in a free state, and various 
compounds of carbon and hydrogen, and compounds of carbon, 
hydrogen, and oxygen. Now the rapid union of chemical ele- 
ments is usually accompanied by the evolution of heat, as in 



FUELS AND COMBUSTION. 57 

the combustion of oxygen and hydrogen. Conversely, heat is 
required to break up a chemical combination. Now the com- 
bustion of a fuel is a complex process, involving usually some 
breaking up of chemical compounds and the union of chemical 
elements with oxygen ; the exact nature of the process is far 
from certain even when the real chemical compounds and ele- 
ments of which the fuel is composed are known. As a rule we 
know only the final analysis of the fuel and do not know the 
compounds which enter into it. For this reason the only 
true way of determining total heat of combustion is by experi- 
ment. Nevertheless it is customary and convenient to make 
a calculation of the total heat of combustion by an arbitrary 
method, when the real heat of combustion of a fuel has not 
been determined. 

Dulong proposed that the heat of combustion should be 
calculated on the assumption that the oxygen in the fuel and 
enough hydrogen to unite with it and form water, could be set 
aside as inert, and that the remainder of the hydrogen and all 
the carbon could be treated as free elements. From the com- 
position of water and the atomic weights of hydrogen and 
oxygen it is clear that each pound of oxygen will require 

2 X 1 i_ 
16 ~~ 8 

of a pound of hydrogen. Dulong's method may therefore be 
expressed by the equation 

Total heat = 14,650 C + 62, 100 (H — £0) 

in which the letters C, H, and O represent the weights of car- 
bon, hydrogen, and oxygen in one pound of fuel. No con- 
fusion need arise because the letters are used with a different 
significance from that given them in chemical formulae. This 
equation does not give very satisfactory results. 



5^ STEAM-BOILERS. 

Mahler has proposed an empirical formula for finding- 
heats of combustions which in French units is 

Total heat = 8 140 C + 34, 500 H — 3000 ( O -f N), 

in which C, H, O, and N represent the weights of the ele~ 
ments carbon, hydrogen, oxygen, and nitrogen in a kilogram 
of fuel. The result is in calories. 

In English units Mahler's equation becomes 

Total heat = 14,650 C + 62, 100 H — 5400 (O -f- N), 

in which the letters represent the weights of the correspond- 
ing elements in one pound of the fuel. The result is in 
B. T. U. This equation gives results that agree very well 
with Mahler's experimental determinations, as shown by the 
table on page 52. 

For example, the total heat of combustion of Pittsburg 
bituminous coal, for which the ultimate analysis in the table 
on page 41 gives 

C == 0.7647, H = 0.0519, O — 0.0810, N = 0.0145. 

appears by Dulong's formula to be 

14650 C + 62, 100 (H -iO) 

... / o.o8io\ 
= 14,650 X 0.764; + 62,100(^0.0519 _ \ 

= 13,720 B. T. U. 

Mahler's formula for the same coal gives 

14,650 c + 62, 100 H -5400 (O + N) 
= 14,650 X 0.7647 -f- 62, 100 X 0.05 19 

— 5400(0.0810+ 0.0145) 
= 13,910 B. T. U. 

Air required for Combustion. — If the moisture and car- 
bon dioxide in the air be neglected, and if, further, the argon 



FUELS AND COMBUSTION. 59 

is not distinguished from the nitrogen, then we have for the 
composition of the atmospheric air, 

By weight j^xygen 0.232 

(Nitrogen 0.768 

„ , ( Oxygen o. 2004. 

By volume K T . y ~T 

( Nitrogen o. 7906 

For rough calculations it is customary to consider that the 
atmosphere is made up of one volume of oxygen and four 
volumes of nitrogen. This approximation is sufficient for 
calculation of air required by fuels, and for similar purposes. 

The air required for combustion of a given fuel may be 
estimated from its composition and from the composition of 
the air. A few examples will make the process clear. 

Thus, carbon burned to C0 2 requires two portions of 
oxygen, so that one pound of carbon will require 



2 X 16 



= 2 



12 



pounds of oxygen. Since air is 0.232 part oxygen by weight, 
one pound of carbon will require 

2%-r- 0.232 — 1 1.5 

pounds of air for complete combustion. 

In like manner one pound of hydrogen will require 

2 

pounds of oxygen, or 

8 -4- 0.232 = 34.5 

pounds of air for complete combustion. 

Another method of calculation is based on the approxi- 
mate composition of air, i.e., one volume of oxygen and four 
of nitrogen. This method depends on the fact that the 



60 STEAM-BOILERS. 

weights of a cubic foot of different kinds of gases are propor- 
tional to their atomic weights ; so that if the weight of a cubic 
foot of hydrogen be taken for the basis or comparison and be 
called unity, then the weight of a cubic foot of oxygen will 
be 16, while that of nitrogen will be 14. We shall then have 
for the approximate composition of air one volume of oxygen 
having the weight 16, and four volumes of nitrogen having each 
the weight 14. In order to get one pound of oxygen we 
must take 

(16 + 4 X 14) -T- 16 = 4i 

pounds of air. 

It has already been shown that one pound of carbon will 
require 2§ pounds of oxygen. By the method just stated it 
appears that a pound of carbon will require 

2§ X 4i = I2 

pounds of air. This result is often quoted and is easily 
remembered. 

Since a pound of hydrogen requires 8 pounds of oxygen, 
this method gives 

3 X A\ — 36 

pounds of air for each pound of hydrogen. 

In calculating the air required for a fuel it is customary to 
use the convention proposed by Dulong for finding heat of 
combustion, namely, that each pound of oxygen in the fuel 
renders one eighth of a pound of hydrogen inert, and that the 
remainder of the hydrogen and all the carbon can be treated 
as free elements. In using this convention it is customary to 
take the approximate weights of air just calculated for a 
pound of carbon and a pound of hydrogen. The convention 
can then be stated in the form of an equation as follows: 

Air per pound ot tuel = 12 C -f- 36 (H — \ O), 



FUELS AND COMBUSTION. 6 1 

In which the letters C, H, and O represent the weights of 
carbon, hydrogen, and oxygen in one pound of the fuel. 
An application of this equation to Pittsburg coal gives 

A- s( 0.08 io\ 
Air = 12 X 0.7647 4- 36(0.0519 — 1 = 10.7 pounds. 

This result is somewhat larger than would be obtained were 
the more exact composition of the atmosphere given on page 
59 used, together with the assumption that the oxygen ren- 
ders inert its equivalent of hydrogen ; but the method is not 
sufficiently well grounded to warrant much refinement. 

As a further illustration of the method the following cal- 
culation of the air required for one pound of defiant gas may 
be interesting. This gas, having the composition C a H 4 , con- 
sists of 

2 X 12 6 

— — — ■ — = — carbon, 

2 X 12 +4 X 1 7 

4Xi 1 u , 
Z = _ hydrogen, 

2 X 12 + 4X 17 
and will require 

■f X 12 + t X 36 — 1 5.4 pounds of air. 

Air for Dilution. — In order to secure complete combustion 
of coal in the furnace of a boiler it is necessary to supply an 
excess of oxygen, or, what amounts to the same thing, an 
excess of air. This excess varies from one half the quantity 
required for combustion to an equal quantity. Thus, roughly, 
from 18 to 24 pounds of air may be furnished per pound of car- 
bon and from 54 to 72 pounds of air per pound of hydrogen. 

Volume of Air for Combustion. — The table on page 55 
gives the density or weight of one cubic foot of the several 
gases mentioned, also the reciprocal of the density or the 
volume occupied by one pound of the gas. This is called the 
specific volume of the gas. The specific volume of air is 
12.39 at the pressure of the atmosphere and at the temper- 



62 STEAM-BOILERS. 

ature 32 F. The volume of a pound of gas increases as the 
temperature rises. At 6o° F. one pound of air will occupy 
about 13 cubic feet. To find the volume of air required per 
pound of fuel we may simply multiply the weight by 13, for 
ordinary calculations. Thus we shall have for the air per 
pound of the principal elements in fuels: 

Without With 50 per With 100 per 
Dilution. cent Dilution, cent Dilution. 

Carbon 150 225 300 

Hydrogen 450 675 900 

These approximate values are sufficient for determining 
the dimensions of doors or passages through which air is 
supplied to the fire. 

This method applied to Pittsburg coal will give, approxi- 
mately, 

10.7 X 13 = 139 

cubic feet of air for each pound of coal without dilution. 
With dilution of 50 per cent the air required will be about 
2IO cubic feet for each pound. 

Sometimes, in connection with boiler-tests or for other 
purposes, a more exact estimate of the amount of air is de- 
sired. The calculation for this purpose can be best explained 
by aid of an example. 

Example. — Required the weight and volume of air needed 
for combustion of Pittsburg coal with 50 per cent dilu- 
tion, the temperature of the atmosphere being 70 F. and 
the height of the barometer being 29 inches, when reduced 
to 32 F. 

This coal is composed of 76.47 per cent carbon, 5.19 per 
cent hydrogen, and 8.10 per cent oxygen. Assuming that 
the oxygen renders inert one eighth of its weight of hydrogen, 
there will be available 

8.10 
5. 19 = 4. 18 per cent 



FUELS AND COMBUSTION. 63 

of hydrogen and 76.47 per cent of carbon. Since one pound 
of carbon requires 2§ pounds of oxygen, and one pound of 
hydrogen requires 8 pounds, the weight of oxygen required 
per pound of coal is 

2% X 0.7647 + 8 X 0.0418 = 2.374 pounds. 

But air contains 23.2 per cent of oxygen by weight, so that the 
air required per pound of coal is 

2.374-^-0.232 = 10.2 pounds. 

The specific volume of air is 12.39, so tnat each pound of 
coal will require 

10.2 X 12.39 — I2 6 

cubic feet of air at the normal pressure of the atmosphere 
and at 32 F. 

To find the volume of air required at the actual pressure 
of the atmosphere and the actual temperature, we have the 
facts that the volume of a given weight of air is inversely pro- 
portional to the absolute pressure and directly proportional 
to the absolute temperature. Now the absolute pressure of 
the atmosphere is 29 inches of mercury as given by the 
barometer, while the normal pressure is 29.92 inches of mer- 
cury. To get the absolute temperature we add 459.5 to the 
temperature by the thermometer; the absolute temperature of 
32 F. is 491.5, and that of 70 F. is 529.5. Under the con- 
ditions of the problem the air required per pound of fuel will 
have the volume, without dilution, of 

^w 5 2 9-5 w 2 9-9 2 

126 X X = 140 

491.5 29.00 

cubic feet. With 50 per cent dilution the volume will be 210 
cubic feet. 

Determination of Air per Pound of Coal. — The amount 
of air supplied per pound of coal may be determined either by 



64 STEAM-BOILERS. 

measuring the air supplied to the furnace or by an analysis of 
the products of combustion. 

For the first method the following arrangement has been 
used in boiler-tests at the Massachusetts Institute of Tech- 
nology : The ash-pit doors are removed and a sheet-iron 
mouthpiece is fitted over the opening into the ash-pit. The 
air for combustion is supplied by a cylindrical sheet-iron con- 
duit leading into this mouthpiece. The area of the conduit 
should be at least equal to the area of the fire-door or fire- 
doors, and its length should be several times its diameter. 
The velocity of the air in the conduit is measured by an ane- 
mometer, from which the volume of air is readily calculated, 
and its weight determined from the temperature and pressure of 
the atmosphere. The joint between the mouthpiece and the 
furnace front must be luted to avoid leakage, and leaks or ad- 
mission of air to the furnace otherwise than through the sheet- 
iron conduit must be stopped or allowed for Anemometers, 
even when tested and rated, are liable to be affected by errors 
of two per cent or more. They are commonly tested by 
swinging them on a revolving arm through still air — a method 
that is proper for small or moderate velocities, but difficult to 
use, and is vitiated by the action of centrifugal force at high 
speeds. An ideal way of testing an anemometer would be to 
find its reading in such a conduit when the weight, and con- 
sequently the velocity, of the air per second is known. The 
weight ma)' be determined by causing the supply of air to 
flow through a well-rounded orifice, to which calculations by 
the proper thermodynamic equations may be applied. This 
method for large conduits would involve the use- of a very large 
air-compressor, which makes it hardly practicable. 

Orsat's Gas Apparatus. — This apparatus, which is well 
adapted to the analysis of flue-gases, determines the propor- 
tion by volume of the carbon dioxide, carbon monoxide, and 
oxygen in a mixture of gases. The remainder of tne flue- 
gases is commonly assumed to be nitrogen, but it includes 



FUELS AND COMBUSTION 



65 



unburned hydrocarbon, if there be any, and steam or vapor 
of water. In Fig. 27, A, B, and C are pipettes containing, 
respectively, solutions of caustic potash to absorb carbon diox- 
ide, pyrogallic acid and caustic potash to absorb oxygen, and 
•cuprous chloride in hydrochloric acid to absorb carbon mon- 
oxide. 

At FFis a three-way cock to control the admission of gas 
to the apparatus ; at D is a graduated burette for measuring 
the volumes of gas, and at P is a pressure-bottle connected 
with D by a rubber tube to control the gases to be analyzed. 
The pressure-bottle is commonly filled with water, but glyc- 




Fig. 30. 



erine or some other fluid may be used when, in addition to the 
gases named, a determination of the moisture or steam in the 
flue-gases is made. 

The several pipettes A, B, and C are filled to the marks a, 
b, and c with the proper reagents, by aid of the pressure-bottle 
P. With the three-way cock IF open to the atmosphere, the 
pressure-bottle P is raised till the burette D is filled with 
water to the mark m ; communication is then made with the 
flue, and by lowering the pressure-bottle the burette is filled 
with the gas to be analyzed, and two minutes are allowed 
for the burette to drain. The pressure-bottle is now raised 
till the water in the burette reaches the zero-mark and the 



66 STEAM-BOILERS. 

clamp k is closed. The valve Wis now opened momentarily 
to the atmosphere to relieve the pressure in the burette. Now- 
open the clamp k and bring the level of the water in the pres- 
sure-bottle to the level of the water in the burette, and take 
a reading of the volume of the gas to be analyzed ; all readings 
of volume are to be taken in a similar way. Open the cock 
a and force the gas into the pipette A by raising the pressure- 
bottle, so that the water in the burette comes to the mark m. 
Allow three minutes for absorption of carbon dioxide by the 
caustic potash in A, and finally bring the reagent to the mark 
a again. In this last operation, brought about by lowering 
the pressure-bottle, care should be taken not to suck the 
caustic reagent into the stop-cock. The gas is again measured 
in the burette and the diminution of volume is recorded as the 
volume of carbon dioxide in the given volume of gas. In like 
manner the gas is passed into the pipette B, where the oxygen 
is absorbed by the pyrogallic acid and caustic potash ; but as 
the absorption is less rapid than was the case with the carbon 
dioxide, more time must be allowed, and it is advisable to 
pass the gas back and forth, in and out of the pipette, several 
times. The loss of volume is recorded as the volume of 
oxygen. Finally, the gas is passed into the pipette C, where 
the carbon monoxide is absorbed by cuprous chloride in hydro- 
'diloric acid. 

The solutions are as follows : 

A. Caustic potash, I part ; water, 2 parts. 

B. Pyrogallic acid, I gramme to 25 c.c. caustic potash. 

C. Saturated solution of cuprous chloride in hydrochloric 

acid having a specific gravity of 1.10. 

The absorption values per cubic centimetre of the reagents 
are — 

A Caustic potash absorbs 40 c.c. carbon dioxide. 

B. Pyrogallate of potassium absorbs 22 c.c. oxygen 

C. Cuprous chloride absorbs 6 c.c. carbon monoxide. 



FUELS AND COMBUSTION. 6 7 

Samples of gas for analysis by Orsat's apparatus should be 
taken from the back of the furnace, from the uptake, and from 
the chimney; the difference in composition of gases at the 
several points will give the basis for calculations of leakage. 

When it is not convenient to draw gases from the flue di- 
rectly into the measuring burette of the apparatus, samples of 
gas may be drawn into glass bottles with rubber stoppers, from 
which gas can be supplied to the burette. 

Calculation from a Gas Analysis. — The calculation of the 
amount of air supplied per pound of carbon and per pound of 
coal, from the known chemical constituents of the flue-gases, 
is best shown by an example. 

Example. — Let it be assumed that the analysis of the flue- 
gases resulting from the burning of Pittsburg bituminous coal 
gives by volume 13 per cent of carbon dioxide, 0.5 per cent 
of carbon monoxide, and 6 per cent of oxygen. It is con- 
venient to treat the percentages by volume as the number of 
cubic feet of the several gases in one hundred cubic feet of flue- 
gas. We will thus have — 

Density. 
Gas. Volume. (See page 55) Weight. 

Carbon dioxide 13 0.12345 1.6043 

Carbon monoxide 0.5 0.07806 0.03903 

Oxygen.,...,. 6 0.08928 0.53568 

Now one pound of carbon dioxide is composed of 

2 X 16 _8_ 

I2-J-2 X l6~ II 

of a pound of oxygen and 3/1 1 of a pound of carbon, and a 
pound of carbon monoxide is composed of 

16 4 

12 4- 16 — 7 

of a pound of oxygen and 3/7 of a pound of carbon. Conse- 
nuentlv we have 



quentiy we have 



68 STEAM-BOILERS. 



r 8 T X 1.6043 


= 1. 1668 


4- X 0.03903 


= 0.0223 




0.5357 



f\ X 1.6043 =0.4375 
f X 0.03903 = 0.0167 



Pounds of oxygen, 1.7248 Pounds of carbon, 0.4542 

And as air consists of 0.232 part by weight of oxygen, the air 
per pound of carbon from the gas analysis is 

1.7248 , . 

—L-l •_ 0.232 = 16.4 pounds. 

0.4542 " * F 

The coal in question contains 76.47 per cent of carbon, 5. 19 
per cent of hydrogen, and 8. 10 per cent of oxygen. Of these 
elements Orsat's apparatus accounts for the carbon only; the 
oxygen and hydrogen together with unburned volatile matter 
pass off with the nitrogen. 

The analysis shows 16.4 pounds of air for each pound of 
carbon ; consequently the carbon in one pound of coal will 
require 

0.7647 X 16.4 = 12.5 

pounds of air. Assuming that the oxygen in the coal renders 
one eighth of its weight of hydrogen inert, and that the re- 
mainder will require 36 pounds of air per pound of hydrogen, 
we shall have 



J 0.08 1 o\ 
36(0.0519 g— ) = 1.5 



of a pound of air required for the hydrogen. So that the 
total air per pound of coal is about 

12.5 + 1.5 = 14 pounds. 

The calculation just given, involving the use of the densities 
of the several gases, is perhaps the most readily understood ; 
there is another method, which gives the same result and is 
more expeditious, depending on the fact that the weight of a 
gaseous compound referred to hydrogen as unity, is half its 



FUELS AND COMBUSTION. fig 

molecular weight. This quantity is called the vapor density of 
the compound. 

Thus the vapor density of carbon dioxide, C0 2 , is 

i(i2 +2 X 16) = 22; 

and the vapor density of carbon monoxide, CO, is 

K12 + 16) = 14. 

Assuming as before that in each 100 cubic feet of flue-gases 
there are 13 cubic feet of C0 2 , 0.5 of CO and 6.0 of O, we 
have for the corresponding weights, based upon hydrogen as 
unity, 

13 x 22 = 286 for C0 2 

0.5 X 14 = 7 for CO 

6.0 x 16 = 96 for O 

Total, 389 

The last result depending on the fact already noted, that the 
weights of elementary gases are proportional to the atomic 
weights. 

Now each pound of C0 2 contains 3/1 1 of a pound of carbon, 
and each pound of CO contains, 3/7 of a pound of carbon, so 
that of the 286 parts by weight of C0 2 we shall have 

T 3 T X 286 = 78 

parts of carbon, and of the 7 parts by weight of CO we shall 
have 

f X 7 = 3 
parts of carbon. The total weight of carbon will be 

78+3 = 8i. 
The weight of oxygen is clearly 

389 — 81 = 308. 



70 STEAM-BOILERS. 

The oxygen per pound of carbon is therefore 

308 -r- 81 = 3.80, 

and the air per pound of carbon is 

308 . 

— -^ 0.232 = 16.4 

pounds, as found by the previous calculation. 

Loss from Incomplete Combustion. — The presence of 
even a small amount of carbon monoxide in flue-gases is evi- 
dence of a very appreciable loss of efficiency, as may be seen 
by the following example, quoted from a test made on a 325- 
horse-power boiler at Lowell. The coal used was George's 
Creek Cumberland, fired by hand. 

An analysis of flue-gases by Orsat's apparatus showed 12.5 
per cent of C0 2 , 1. 1 per cent of CO, and 4.1 per cent of O, 
by volume. 

Using the method of vapor densities for making the calcu- 
lation, it appears that the C0 2 contained 

T 3 T x 12.5 X 22 = 75 parts of carbon, 
and the CO contained 

f X I- 1 X 14 = 6.6 parts of carbon. 
Now 75 pounds of carbon burned to C0 2 gives 
75 x 14,650 = 1,098,750 B. T. U., 
and 6.6 pounds of carbon burned to CO gives 
6.6 X 4400 = 29,040 B. T. U., 

or a total for all the carbon of 1, 127,790 B. T. U. 

Had all the carbon been burned to C0 2 , the heat of com- 
bustion would have been 

(75 -f 6.6) 14,650 = 1, 195,440 B. T. U. 



FUELS AND COMBUSTION. 7 1 

The loss by incomplete combustion was consequently 

1,195,440—1,127,790 . 

yD '^ ! — /,/y x 100 =5.6 per cent. 

1,195,440 

The actual loss may be placed at a little less figure than 5.6 
per cent, since less air is required for burning carbon to CO 
than for C0 2 . 

Loss from Excess of Air. — The ideal condition would be 
to supply just enough air to burn all the carbon in the coal to 
CO a and all the free hydrogen to H 2 ; it is necessary to use 
somewhat more air than required for complete combustion to 
avoid the formation of CO and the attendant loss of heat. On 
the other hand, too great an excess of air occasions a loss, as 
that excess must be heated to the temperature in the chimney. 

As an example, suppose that Pittsburg coal can be com- 
pletely burned with 50 per cent excess of air, but that 100 per 
cent excess is allowed to pass through the grate. 

To simplify the problem we will neglect the effect of sul- 
phur and of the ash, more especially as it is not certain what 
their effect is ; we know only that it cannot be very impor- 
tant. 

Each pound of carbon will yield 3§ pounds of C0 2 and 
each pound of hydrogen will yield 9 pounds of H 2 0. There 
will therefore be 

3f X 0.7647 — 2.8039 pounds of C0 2 ; 
9X0.0519 = 0.4671 " " H 2 0. 

In the calculation for the weight of air (page 63) it has 
been shown that 2.374 pounds of oxygen and 10.2 pounds of 
air are required for combustion. There is therefore 

10.2 — 2.374 = 7.826 

pounds of nitrogen in the air for combustion. But each 
pound of coal contains 0.014 °f a pound of nitrogen, so that 
the total nitrogen is 7.840 pounds. 



72 STEAM-BOILERS. 

Now the heat required to raise the temperature of one 
pound of a substance one degree, called the specific heat, is 
given in the table on page 55. For carbon dioxide the specific 
heat is 0.2169, an ^ * ne neat required to raise 2.8039 pounds 
one degree is 

2.8039 X 0.2169 = 0.6082 B.T. U. 

The following are the calculations for the several compo- 
nents of the products of combustion : 

Weight. specific 

Carbon dioxide, C0 2 2.8039X0.2169 = 0.6082 B. T. U. 

Steam, H a O. 0.4671 X 0.4805 = 0.2244 " 

Nitrogen 7.840 X 0.2438 = 1. 91 14 C( 

Air for dilution 50$.... 5.100 X 0.2375 = 1.2 112 ec 



Total 3>955 2 



a 



If the external air is at 6o° F., and the gases in the chim- 
ney are at 560 F., then the heat in the chimney-gases above 
the temperature of the air is 

500 X 3.9552 = 1978 B. T. U. 

The total heat of combustion of this coal by Duiong's 
formula is 13800 B. T. U. ; of this about 10 per cent will be 
lost by conduction and radiation. There will then remain to 
be transferred to the water in the boiler 

13800 — (1380 -f 1978) = 10442 B. T. U. 

This is about y6 per cent of the heat generated by combus 
tion, 

Suppose that the dilution is allowed to be 100 per cent, 
so that 5 additional pounds of air per pound of coal are ad- 
mitted to the grate. Then to the above total must be added 






FUELS AND COMBUSTION. 73 

1.2 1 12 B. T. U., making in all 5.1664 B. T. U. Multiply- 
ing by 500, the difference of temperature assumed 

500 X 5- 1664 = 2583 B. T. U. 

Assuming, as before, 10 per cent for loss by radiation and 
conduction leaves 

13800 - (1380+2583) = 9837 B. T. U. 

to be transferred to the water in the boiler. This is about 72 
per cent, so that the loss by the excess of dilution is about 4 
per cent. 

Hypothetical Temperature of Combustion, — A calcula- 
tion is sometimes made of the temperature of the fire on the 
assumption that the total heat of combustion is all applied to 
raising the temperature of the products of combustion, includ- 
ing the ash. In the case of Pittsburg coal it has been found 
that 3.9552 B„ T. U. are required to raise the products of 
combustion one degree, allowing 50 per cent for dilution. 
This coal has y.6 per cent ash, for which a specific heat of 0.2 
may be allowed. We must therefore add to the total just 
quoted 

.076 X 0.2 == 0.0152 B. T. U., 

making in all 3.9704 B. T. U. Dividing the total heat by 
this quantity, we get 

13800 -h 3.9704 = 3480 F. 

for the elevation of temperature. To this we will add the 
temperature of the air admitted to the furnace, say 6o° F., 
making 3540 F. for the hypothetical temperature of the 
fire. 

Such a temperature is never reached in the furnace of a 
boiler, for the combustion is not instantaneous and is not 
completed in the furnace, as flames commonly extend over 



74 STEAM-BOILERS. 

the bridge-wall or into the combustion-chamber; meanwhile 
there is an energetic radiation from the glowing fuel and 
flame, and a rapid transfer of heat from the hot gases to the 
heating-surface of the boiler. The better the fuel and the 
higher the hypothetical temperature of the fire the less chance 
is there that the actual temperature will approach it. 

During a test on a Babcock & Wilcox boiler, at the 
Massachusetts Institute of Technology, it was found that the 
temperature immediately over the fire was about II00°F., 
while the temperature in the chimney was 400 F. 

A test on a boiler of the locomotive type, at the Boston 
Main Drainage Station, gave for the temperature of the gases 
escaping from the boiler 439 F., while the steam in the 
boiler was about 337° F. The gases were afterwards reduced 
to 1 94 F. by passing them through a feed-water heater. 
This boiler was designed for and gave a high efficiency, and 
the results obtained may be considered to represent first-rate 
practice. 

Volume of a Ton of Coal. — 

Kind of Coal. Cubic Fee; to Ton. 

Soft coal 41 to zj3 

Buckwheat or pea 37 

Nut 34 

Furnace size 36 

Coke 76 



CHAPTER IV. 
CORROSION AND INCRUSTATION. 

THE water supplied to a boiler for forming steam may 
corrode the iron of the boiler, or it may deposit material that 
can form a scale or incrustation; both actions may go on at 
the same lime. 

Pure water, free from air and carbon dioxide, has little or 
no solvent action on iron, even though some other metal, 
such as copper, which may with the iron form the elements of 
a galvanic couple, be present. On the other hand, iron will 
not rust if placed in an atmosphere of dry air or dry carbon 
dioxide. All natural water, rain-water, water from wells, rivers, 
lakes, or the sea, contains air in solution, and carbon dioxide 
is not infrequently found in such waters. Iron is rapidly 
acted upon by water containing air or carbon dioxide, and, on 
the other hand, iron rusts rapidly in air or carbon dioxide when 
moisture is present. Again, distilled water, as from the sur- 
face condenser of a marine engine containing more or less oil, 
or the substances resulting from the action of steam on oil, 
causes corrosion in boilers that are free from scale. To avoid 
rusting of boilers when not in use they ought to be either 
quite dry inside or they ought to be entirely filled with 
water — preferably water that has been freed from air by boil- 
ing. In the American Navy it has been the custom to dry 
out boilers and paint them inside with mineral oil preparatory 
to laying them up. In the English Navy the boilers are 
dried out, a pan of glowing charcoal is placed in the boiler to 

75 



76 



5- TEA M- BOILERS. 





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CORROSION AND INCRUSTATION. 77 

consume the oxygen of the air, and quicklime is introduced 
to absorb moisture. 

Mineral Impurities. — The impurities found in water sup- 
plied to land boilers are commonly carbonate of lime and 
sulphate of lime, with more or less organic matter, and some- 
times sand or clay held in suspension. The table on page 76 
gives the number of grains of various mineral substances held 
in solution in water from several sources. 

Water supplied to land boilers is either hard or soft ; the 
first contains appreciable quantities of lime, and the other 
usually contains little solid matter of any sort. The first three 
examples in the table on the preceding page may be taken as 
typical soft waters, and all the others, except the last two, as 
typical hard waters. While there is considerable difference 
in the amounts and the composition of the solids in solution 
in the several examples of hard water, it will be seen that 
they are all characterized by a considerable amount of calcium 
and magnesium carbonates, and (with the exception of Nos. 6 
and 9) accompanied by a comparatively small amount of cal- 
cium and magnesium sulphates. It will be noticed that Mis- 
souri River water is distinctly worse than Mississippi River 
water, not only in that it contains more of the carbonates, 
but because it contains a considerable quantity of sulphates. 
No. 9, from a well at Downer's Grove on the C, B. and Q. 
R. R., a few miles from Chicago, has been selected as an 
example of a very bad hard water, especially as it contains so 
much sulphate. The reason for considering the sulphates of 
lime and magnesia so deleterious will appear a little later. 
Note will be made that the water from the Mississippi River 
at two different places, and presumably at different seasons of 
the year, vary considerably, especially in the amount of mat- 
ter held in suspension. 

In some places in the western parts of the United States 
the only available waters for making steam are strongly im- 
pregnated with alkalies and borax. Such waters have so 



78 STEAM-BOILERS. 

deleterious an action on boilers that the advisability of using 
a surface condenser, as at sea, the distillation of water by a 
multiple-effect evaporator, or the introduction of a supply of 
good water even from remote places, is worthy of considera- 
tion. If the use of such water cannot be avoided, a competent 
chemist should be consulted to suggest methods for ameliorat- 
ing the bad effects so far as possible. As each case is liable 
to require special treatment, no further discussion appears 
profitable in this place. 

The carbonates of lime and magnesia are held in solution 
in water by an excess of carbon dioxide and are completely 
precipitated by boiling. They are thrown down from water 
supplied to a boiler, in the form of a white or grayish mud, 
provided there are not other impurities that cement them to 
gether and form a hard scale. The customary and sufficient 
method of treating boilers supplied with water containing car- 
bonates of lime and magnesia is to let the boiler, while full, 
ccol down, and then run out the water and thoroughly wash 
out the boiler with a strong stream from a hose. If the water 
is blown out under steam-pressure the deposits are hardened 
and are removed with difficulty. While pure carbonates are 
easily treated as just described, the presence of other impu- 
rities, such as oil or organic matter, or of sulphate of lime, is 
likely to make the deposits hard and adhering. 

Sulphate of lime is much more soluble in cold than in hot 
water, and is entirely thrown down from water at a tempera- 
ture of 280 F., corresponding to 35 pounds pressure of steam 
above the atmosphere. It forms a hard and adhering scale, 
and even in comparatively small quantities has a bad effect on 
scales and deposits composed of carbonates, as has already 
been suggested. The bad effect of deposits from water con- 
taining calcium sulphate is much ameliorated by introducing 
carbonate of soda or soda-ash into the boiler with the feed- 
water. The result is to give a deposit of calcium carbonate 
in the form of a fine white powder, which must be washed 



CORROSION AND INCRUSTATION. 79 

or swept out, and sodium sulphate in solution, which must be 
blown out from time to time. 

If the mineral matters in the water are known from a 
chemical analysis, the quantity of carbonate of soda to be used 
may be calculated as follows: 

£xamp/e.—Find the weight of carbonate of soda required 
per day for a boiler supplied with 1000 gallons of water per 
day from the well at Downer's Grove. 

From the table on page 66 it appears that each gallon of 
the water contains 14.037 grains of CaS0 4 and 25.422 grains 
of MgS0 4 . The formula for soda crystals being Na 2 C0 3 + 
ioH 2 0, the reactions, neglecting the water of crystallization, 
will be 

CaS0 4 + Na 2 C0 3 = CaC0 3 + Na 2 S0 4 ; 
MgS0 4 + Na 2 C0 3 = MgCO, + Na 2 S0 4 . 

If x x is the grains of carbonate of soda to act on the cal- 
cium, we have 

CaS0 4 ;Na s C0 3 + ioH 2 = 14.037 : x x ; 
40+32 +4 X 16 : 2 X 23 + 12 + 3 X 16+ 10(2 -f 16) 

= 14.037:^. 
.*. x x = 29.52 grains. 

The magnesium sulphate which is soluble is also changed 
into the carbonate and thrown down as a white precipitate, 
adding to the deposit. The number of grains of carbonate 
of soda required for this reaction is found as follows : 

MgS0 4 : Na 2 C0 3 + ioH 2 = 25.422 : x 2 ; 
24+ 32 +4 X 16: 2 X 23 + 12 + 3 X 16+10(2+16) 
= 25.422: x v 
.'. x 2 = 60.59 grains. 

The total weight of carbonate of soda per gallon is therefore 
29.52+60.59= 90+, 



80 STEAM-BOILERS. 

and the weight required for iooo gallons is 
90 X 1000 



7000 



= 12.9 pounds per day. 



It is advisable that soda, or any other chemical for acting 
on the impurities of feed-water, shall be introduced at regular 
intervals. Sometimes a weight, or measured portion, is thrown 
into the feed-water in a tank or reservoir, from which it is 
pumped. Sometimes the chemical, dissolved in water or 
diluted with water, is placed in a small tank or receptacle that 
may be temporarily connected with the suction of the feed- 
pump. If this method is used care must be taken not to 
admit air to the pump and so derange its action. 

Soda-ash is commonly used instead of carbonate of soda, 
as it is cheaper and somewhat more efficient, on account of the 
caustic soda it may contain. Its chemical composition is 
uncertain, and it is therefore impossible to make satisfactory 
calculations for the quantity to be used. This, however, is 
commonly no real objection, for we seldom have a chemical 
analysis of the water, and cannot determine directly how much 
soda is required. 

An excess of soda in a boiler is liable to cause foaming, 
and at high temperatures, corresponding to pressures now ha- 
bitual for steam-boilers, the soda is apt to attack the inside of 
water-glasses ; any indication of either action should raise the 
question whether too much soda is used, but the absence of 
such an indication does not show that we are using the right 
quantity. When a hard scale is formed by a water known to 
contain lime, we may infer that sulphates are present, and may 
find by trial the amount of soda to be used. Unfortunately 
other impurities, such as organic matter, cause the formation 
of hard scale, and make this method uncertain. Such impur- 
ities often produce discoloration, and thus betray their pres- 
ence. The deposits of lime, whether carbonates or sulphates 
are commonly white or grayish, or sometimes fawn color. 






CORROSION AND INCRUSTATION. 8 1 

It is sometimes proposed to use ammonium chloride, or 
sal-ammoniac, to break up lime compounds; in the first 
place, only the carbonates are acted upon by this reagent, 
and in the second place, the reagent itself, or the resultant 
chlorides, are liable to be broken up, giving free chlorine, 
which attacks the boiler. 

Tannic acid, either commercial acid or in the crude state, 
may be used to break up a scale already formed ; but as 
tannic acid does not decompose the sulphates , and as the 
compound of the acid with lime is not soluble, its use appears 
to be restricted. Many proprietary boiler compounds depend 
on tannic acid for their action. Acetic acid may also be 
used to break up the carbonates, but it likewise has no action 
on the sulphates ; the carbonates are changed into soluble 
acetates, and can be blown out. Both tannic acid and acetic 
acid attack iron, but are not so dangerous as sulphuric or 
hydrochloric acids, which are sometimes recommended for 
breaking up scale. When a scale is once formed the safer 
way is to remove it with proper chipping and scaling tools; 
but this will be found to be impossible for many types of 
boilers unless they are largely dismembered for that purpose. 

When river-water is used in boilers, various earthy im- 
purities are liable to be carried into boilers, such as clay and 
sand, together with soluble matters. Even waters from 
ponds or wells may contain considerable matter in suspension. 
Such substances can sometimes be removed by filtering or by 
allowing the water to stand so that the insoluble matter may 
be deposited. Very commonly a systematic blowing out 
from the surface of the water and the bottom of the boiler 
will remove such impurities from the boiler. If, however, 
lime and magnesium carbonates and sulphates are present, 
suspended matter is carried into the scale, and the scale may 
be made more troublesome in consequence. The carbonates 
are more likely to form a hard scale if any binding material 
such as clay, is present. 



82 



S TEA M-BOILERS. 



Fig. 31 shows the section of a feed-pipe which was nearly 
choked with scale from lime-water. Though the deposit of 
scale in a horizontal piece of feed-pipe where the water may 
be heated by conduction and otherwise, especially during 
intervals of feeding, is probably more rapid than in the boiler 
itself, this may serve to call attention to the extent to which 
scaling may occur when precautions are not taken. 




Fig. 31 .* 

Lime-extracting Feed-water Heater. — It has been 
pointed out that carbonate of lime can be completely pre- 
cipitated by boiling to drive off the excess of carbonic acid ; 
carbonate of magnesia if present is thrown down at the same 
time. Also sulphate of lime is thrown down at 280 F., cor- 
responding to 35 pounds pressure above the atmosphere. 
It is evident that lime compounds can be removed from feed- 
water by heating it and removing the precipitated lime before 
feeding it to the boiler. For this purpose we may use a 
heater such as the Hoppes heater and purifier shown by Fig. 
32, which consists essentially of a series of cylindrical pans 



* This figure and Figs. 35 to 38 were kindly loaned by the Hartford Ste^ro 
Boiler Inspection and Insurance Co. 



CORROSION AND INCRUSTATION. 



83 



of sheet steel, 1, 2, 3, 4, 5, and 6. The feed-water is pumped 
into the upper pan, from which it overflows, and, trickling 
along the bottom, it drops into the pan 2. From 2 the 
water overflows into 3, and so on. 

The capacity of the heater depends on the number of 
sets of pans, which varies from one to four. The pans are 
enclosed in a steel shell, from which one end may be removed 
for cleaning the pans. Feed-water is pumped in at B; steam 
from the boiler is admitted at A ; the feed-water after being 
heated and purified runs out at D on the way to the boiler; 




Fig. 52. 

at C there is a blow-out, from which air and gases may be 
blown out when the heater is started, or at other times. 

It is desirable that the pipe D shall drop down below the 
water-level in the boiler before any turns or horizontal pipes 
are attached. The water runs from the heater to the boiler 
by gravity only, and the heater must be placed high enough 
for this purpose. It is also desirable that the feed-pump be 
supplied with steam from the heater so as to continually 
remove the carbonic acid, air, or other gases given off from 
the feed-water. 



84 



S TEA M-B OILERS. 



The feed-water as it trickles along the under sides of the 
pans in a thin film is heated by the steam, and the lime com- 
pounds are deposited in form of a scale or incrustation, 
Meanwhile mud, sand, and other mechanical impurities settle 
to the bottom of the pans. 

After the heater has been at work a month or so, depend- 
ing on the amount of lime in the water, the pans must be 
removed and cleaned. The steam-pipe and the pipe leading 
to the boiler are shut off by proper valves, and cold water is 
pumped in and allowed to run to waste at the blow-off. The 
contraction of the pans cracks off hard scale and makes it 
easier to remove. When the heater is first opened the scale 
is usually soft and can be readily removed ; it is liable to 
harden when exposed to the air and allowed to dry. 

A heater for use with exhaust-steam, by the same makers, 
differs from this mainly in that there is a device for extract- 
ing oil from the steam before it meets the feed-water, and in 
that it is run at atmospheric pressure. Such a heater will not 
remove sulphate of lime ; and further, since it is difficult if 
not impossible to remove oil from exhaust-steam, it is proba- 
ble that some oil will be carried over into the boiler. 

Sea-water. — The following table gives an analysis of sea- 
water by Professor Lewes of the Royal Naval College, to- 
gether with an analysis by him of a typical boiler deposit from 
a marine boiler: 

SALTS IN SEA-WATER AND COMPOSITION OF MARINE- 
BOILER SCALE.* 



Marine-boiler 

Scale. 

Per Cent. 



Calcium carbonate (chalk). . 
Calcium sulphate (gypsum). 

Magnesium sulphate 

Magnesium chloride 

Magnesium hydrate 

Sodium chloride (salt). . . . 

Silicia (sandy matter) 

Moisture 



* Trans. Inst. Naval Arch. 




P- 330. 



CORROSION AND INCRUSTATION. 85 

The three principal constituents of the marine scale are cal- 
cium sulphate, calcium carbonate, and magnesium hydrate, 
of which the first forms the greater part of the scale. 

The calcium carbonate is kept in solution by the carbonic 
acid in the sea-water, just as is the case for fresh water con- 
taining carbonate of lime, and is deposited when the carbonic 
acid is driven off by heat. There is, however, a reaction 
between the calcium carbonate and magnesium chloride at the 
temperature and pressure in the boiler, giving a deposit of 
magnesium hydrate and leaving calcium chloride in solution, 
so that only part of the calcium carbonate appears in the scale ; 
and on the other hand, we may thus account for the presence 
of the magnesium hydrate in the scale. 

The calcium sulphate forms so large a part of the scale, that 
we will give attention to it only in the further discussion. Cal- 
cium sulphate is more soluble in water at 95 ° F. than at any 
temperature higher or lower; and the solubility decreases with 
the rise of temperature, till at about 280 F., which corre- 
sponds to 50 pounds pressure absolute to the square inch, or 
35 pounds above the atmosphere, the entire amount of cal- 
cium sulphate is deposited. In the early history of the marine 
engine, when low pressures of steam prevailed, we find jet con- 
densers in use, and the boilers, which were fed from the brine 
in the hot-well, were kept fairly free from scale by blowing 
out the concentrated brine. It was then customary to supply 
half again as much feed-water as was evaporated, the excess 
being compensated by the concentrated brine blown out, and 
the water in the boiler had three times the degree of concen- 
tration found in the sea. As high-pressure steam came into 
use, surface condensers became indispensable. When surface 
condensers first came into use the waste of steam from leakage 
and otherwise was made up from water taken from the sea, 
with the result that the boilers gradually accumulated a heavy, 
dense scale. Since it is customary. to have an auxiliary boiler, 
called a donkey-boiler, on steamships, the first device to avoid 
the scaling from the use of sea-water in the main boilers appears- 



86 STEAM-BOILERS. 

to have been to supply the loss of steam from the donkey- 
boiler, which was fed from the sea. This of course only trans- 
ferred the difficulty from one place to another, even though a 
less objectionable one. At present the loss is made up by 
vaporizing sea-water in a special boiler, which is heated by 
steam-coils supplied with steam from the main boilers. The 
pressure may be low enough in this vaporizer to avoid the 
total precipitation of the calcium sulphate, and the brine may 
be kept at any desirable degree of saturation by blowing out, 
as in the early marine practice; and further, the vaporizer is 
so made that the steam-coils may be readily cleared from 
scale. 

It should be pointed out that the decomposition of the 
calcium sulphate in sea-water by the aid of soda is impracti- 
cable, on account of the large quantity of magnesium carbonate 
thrown down by reaction on the magnesium sulphate. 

A boiler fed with water condensed in a surface condenser, 
as is now common in marine practice, is liable to two diffi- 
culties : (i) the distilled water is apt to corrode or pit the plates 
of the boiler, and (2) the cylinder-oil used in the engine is 
liable to be carried over into the boiler and form oily scales 
and deposits. 

When sea-water is used in the boiler, either as the main 
boiler-feed or merely to supply the waste, the boiler-plates are 
protected by the scale of calcium sulphate, and general corro- 
sion or local pitting is seldom troublesome. When care is 
taken to avoid the use of salt water, supplying the waste with 
fresh water from a distiller or otherwise, general corrosion and 
local pitting have both been found to occur to a dangerous 
degree. A simple remedy appears to be to form a very thin 
scale by the use of sea-water, and then avoid further use of 
sea-water. It is, however, found that water from a surface 
condenser will gradually dissolve off such a scale, and it must 
be occasionally renewed. There is also an objection to the 
introduction of any lime compound into a boiler, as wili appear 






CORROSION AND INCRUSTATION. 87 

in the discussion of the difficulty from the collection of oil in the 
boiler. In both the United States and the English navies it is 
customary to use slabs of zinc to protect the boiler-plates from 
corrosion. The zinc is fastened to or hung from the boiler- 
stays, with which metallic connection should be made to in- 
sure galvanic action. The zinc is gradually consumed, and 
becomes soft and friable, so that the slabs require renewal. 
It is recommended to supply 1/4 of a pound of zinc for each 
square foot of grate-surface. 

It is a familiar fact that the cylinders of an engine may be 
oiled by introducing the oil into the supply-pipe, and that the 
oil will be carried quite thoroughly over the surface of the 
cylinder by the steam ; and, further, that the oil is carried out 
of the cylinder by the steam, and will appear in the condensed 
water in the hot-well. It is evident that any oil is liable to 
be injurious if it gets into a boiler. It is, consequently, cus- 
tomary to filter the water from a surface-condenser, to remove 
the oil as far as possible. For this purpose sponges have 
been used in the navy; they, of course, must be occasionally 
taken out and washed free from oil. A very simple and effi- 
cient filter has been made in the form of a rectangular box, 
with perforated plates near the ends ; the water from the hot- 
w T ell runs into one end compartment, passes through a mass of 
hay in the middle compartment, and is drawn from the further 
end compartment by the feed-pump. When the hay becomes 
foul it is thrown away, and fresh hay is put in. Professor 
Lewes advises for a filter a long tube filled with charcoal 
about the size of a walnut ; of course the charcoal should be 
renewed when necessary. It cannot be expected that any 
system of filtering will remove all the oil from the water, but 
the larger part may be removed. It is advisable that no more 
oil than necessary shall be used in the cylinders of the engine. 

Professor Lewes * gives the following account of an inves- 

* Trans. Inst. Nav. Arch., xxxii. page 67. 



88 S TEA M-B OILERS. 

ligation of the collapse of the furnace-flues of a large Atlantic 
steamer, which made the voyage in twelve days : 

The boilers were five and a half years old, and were refilled 
with fresh water at the end of each voyage, while the waste of 
the voyage was made up by the use of about 70 tons of fresh 
water, but during the last voyage sea-water was used for this 
purpose. Every four hours, while under steam, four pounds 
of soda crystals were put in the hot-well, making two hundred- 
weight during the run, the total capacity of the boilers being 
81 tons. For lubricating purposes seven pints of valvoline 
were used in the cylinders every four hours. 

When in port the boilers were allowed to cool down, and 
the water was run off and they were swept down with stiff 
brushes, and were afterwards sluiced out with a hose shortly 
before being filled with fresh water. No trouble occurred 
until five voyages before the final collapse, when some of the 
furnaces began to creep in : they were stiffened with rings and 
stays ; and on succeeding voyages the whole of the furnaces 
got out of shape one after the other. Examination showed 
that they had never been very heavily scaled. On the furnace- 
crown there was only a slight white scale not more than 1/64 
of an inch thick, while on the bottom of the furnaces there was 
a brown oily deposit 1/16 of an inch thick, which in other 
parts of the boiler increased to 1/8 or 3/16 of an inch. 

The valvoline was a pure mineral oil with a specific gravity 
of 0.889 an d a boiling-point of 37 1° C. 

The composition of scales from several parts of the boiler 
is shown in the table on the next page. 

Careful examination of the organic matter and oil in these 
deposits showed that half of it was valvoline in an unchanged 
condition, which had collected around small particles of calcic 
sulphate. 

All the deposits were rich in oily matter except the top 
of the furnaces, i.e., the place where the collapse occurred. 
There the scale was not only nearly free from oil, but per- 
fectly harmless both in quantity and quality. It appeared 



CORROSION AND INCRUSTATION. 
COMPOSITION OF DEPOSITS IN A MARINE BOILER. 



Calcium sulphate 

Calcium carbonate 
Magnesium hydrate . . . 
Iron, alumina, siiica. . . 
Organic matter and oil 

Moisture 

Alkalies 





So; 




> 




H 




O 




5 


H 


.£3 - 
^ 5 ■» 


6 3 


CO 3 

So 

fcu 




a 
u 

en 


- m iu 

u 3 

Q 


84.87 


59-n 


50.92 


II.60 


5.90 


6.07 


4.18 


O.82 


2.83 


11.29 


14.12 


22.21 


2-37 


2.85 


7-47 


9.14 


3-23 


19-54 


2I.o6 


50.20 


80 


1. 14 


1. 17 


4- 23 






I.08 


1.80 



0~ 

P o 



li 



entirely improbable that the scale on the top of the furnaces 
could be in its original condition. 

When oil has entered a boiler the minute globules, if in 
large quantity, coalesce to form an oily scum on the surface, 
or if in small quantity remain in separate drops, but show no 
tendency to sink on account of their low specific gravity. 
They, however, come in contact with solid particles of calcium 
sulphate, coat them with oil, and so the light oil becomes 
loaded till it is easily carried along by convection-currents and 
adheres to surfaces with which it comes in contact, which 
are quite as likely to be the under surfaces of tubes as the 
upper surfaces. Since some brine is liable to find its way to 
the boiler, from leakage into the condenser or otherwise, even 
when sea-water is not used directly, this action will occur in 
a boiler supposed to contain fresh water only. 

The deposits thus formed are very poor conductors of -heat, 
and the oily surface interferes with contact with water. On 
the crown of the furnace this soon leads to overheating of the 
plates, and the deposit begins to decompose, the lower layer 
in contact with the plate giving off gases which blow up the 
greasy layer, ordinarily only 1/64 of an inch thick, to a spongy 
mass 1/8 of an inch thick, which, because of its porosity, is even 
a better non-conductor of heat than before, and the plate be- 
comes heated to redness and collapses. During the last stages 



9° STEAM-BOILERS. 

of this overheating the temperature has risen to such a point 
that the organic matter, oil, etc., in the deposit burns away, 
or is distilled off, leaving behind, as an apparently harmless 
deposit, the solid particles round which it had originally formed. 

Such a deposit is more likely to be produced in boilers 
containing fresh or distilled water, as the low density of the 
liquid enables the oily matter to settle more quickly, while 
with a strongly saline solution it is very doubtful if this sink- 
ing-point would ever be reached ; it is evident also that when 
oil has found its way into the boiler and is causing a greasy 
scum on the surface the most fatal thing that can be done is 
to blow off the boilers without first using the scum-cocks, be- 
cause as the water sinks the scum clings to the tops of the fur- 
naces and other surfaces with which it comes in contact, and 
on again filling up with fresh water it still remains there, 
causing rapid collapse. A very remarkable instance of this 
is to be found in the case of a large vessel in the Eastern trade, 
in the boiler of which an oil-scum had formed. The ship 
having to stop some days in Gibraltar, the engineer took the 
opportunity of blowing out his boiler and refilling with fresh 
water, with the result that before he had been ten hours under 
steam the whole of the furnaces had collapsed. Under some 
conditions the oil-coated particles coalesce and form a sort of 
floating pancake, which, sinking, forms a patch on the crown 
of the furnace at one particular spot, and under these condi- 
tions the general result is the formation of a pocket. 

A curious fact is that these oily deposits are found to con- 
tain a considerable amount of copper. Even mineral oils have 
a solvent action on copper and its alloys, and it is evident 
that the copper in the oily deposits has been obtained from 
the fittings of the cylinder and condenser. Fortunately this 
copper is protected by oil, otherwise serious galvanic mischief 
would result. 

Professor Lewes found from experiment that a coating, 1/16 
of an inch thick, of the oily deposit found in the bottom of a 



CORROSION AND INCRUSTATION. 91 

boiler, applied to the inside of a clean iron vessel, very greatly 
retarded the transmission of heat from a Bunsen flame, as 
shown by the time required to heat a known quantity of water 
to boiling-point. Using an atmospheric blowpipe, he succeeded 
in raising the outside surface of the vessel, when coated with 
1/16 of an inch of the deposit, to the temperature of the melt- 
ing-point of zinc, and with an oxy-coal-gas flame he fused a 
hole in the bottom of a thin wrought-iron vessel thus coated 
and filled with water. 

He further says that cylinders should be sparingly lubri- 
cated with a pure mineral oil having a high boiling-point, and 
that animal or vegetable oil should never be used, because 
they are decomposed by the action of high-pressure steam, 
producing fatty acids that attack iron, copper, and copper 
alloys. 

Professor Lewes has proposed that marine boilers at sea 
shall have the water supplied with brine from which the lime 
compounds have been precipitated in a closed receptacle by the 
combined action of heat and carbonate of soda. The resulting 
brine contains mainly sodium and magnesium chlorides and 
magnesium sulphate, which do not form scale even though the 
concentration is carried to a higher degree than would occur 
from the supply of the waste of the boiler in this way for a 
voyage of some length. This method has not as yet been 
adopted in practice. Attention is called to the fact that an 
excess of soda should be avoided, since it would cause a bulky 
deposit from the action on the magnesium sulphate brought in 
by leakage of sea-water into the condenser. A description of 
the apparatus for producing this brine without lime salts is 
given in the " Transactions of the Institution of Naval Archi- 
tects" (see the reference, page 84). 

Organic Impurities. — Water for feeding boilers, unless 
taken from a contaminated source, seldom contains much 
organic matter. Surface water from rivers or ponds may con- 
tain some vegetable matter, but if there are no other impuri- 



02 



S TEA M-B OILERS. 



ties such organic matter will not cause much trouble unless it 
is allowed to accumulate. The vegetable and other organic 
impurities commonly float on the surface of the water when 
the boiler is making steam, or are carried around by convec- 
tion-currents, and may be blown out through a surface blow- 
out, shown by Fig. 33. It consists essentially of a flattened 




Fig. 33. 

bell or cone of sheet metal extending across the boiler at the 
water-level, and turned so that the convection-currents will 
carry and lodge floating substances in the mouth of the bell. 
The valve in the pipe leading from this bell may be opened 
from time to time to blow out the substances collected in it. 

When a boiler has been at rest for some time, overnight 
for example, the various solids in the boiler, if heavy enough, 
will settle to the bottom, and may be advantageously blown 
out before starting the boiler into action again. This may be 
accomplished by opening the blow-out valve or cock for a short 
time, until the water-level falls a few inches. 

Water from bogs frequently contains vegetable acids that 
are likely to corrode the plates of the boiler: in such cases 






CORROSION AND INCRUSTATION. 



93 



carbonate of soda may be used to neutralize the acids; the 
proper amount must be found by trial. 

The oil used in the engine is liable to get into the boiler 
if surface-condensing is made use of; this subject has already 
received attention in connection with the discussion of marine- 
boiler incrustations. Surface condensers are not commonly 
used in land practice, except with turbines. The exhaust-steam 
from non-condensing engines is used for heating in radiating- 
coils, and there is an apparent gain from the use of the warm 




Fig. 34. 



water from the return-pipes. This water is, however, liable 
to be contaminated by oil, and the oil when it gets into the boiler 
may cause serious damage, such as was found to occur in marine 
boilers. If the feed-water has a little vegetable matter in it, the 
effect of the oil is much worse than if the water-supply is pure. 
Again, the oil is very troublesome if the water contains lime 
salts. The bad effect of oil or other impurities on lime-scale 
has been already noted. Usually it will be found better to 
ieject the water returned from a heating system supplied with 
exhaust-steam, as the apparent economy is liable to be 
more than counterbalanced by damage to the boiler. The 



94 S TEA M-B OILERS. 

externally-fired tubular boilers commonly used in this part of 
the country are liable to bulge in the sheets over the furnace, 
as shown in Fig. 34, if oil gets into them. When the plate 
is cut out a hard deposit of oil, commonly mixed with other 
impurities, will be found adhering to the plate; this deposit 
is a very poor conductor of heat, and it causes so much over- 
heating of the plate that it bulges out under the pressure of 
the steam. 

In isolated cases it will be found that water of a stream 
may be so contaminated with chemicals from some industrial 
establishment that it acts energetically on the boiler-plates ; 
in such case the water must be abandoned unless the contam- 
ination can be stopped. 

Kerosene and Petroleum Oils.— Both crude petroleum 
and refined kerosene have been used in steam-boilers to miti- 
gate the effect of incrustations of calcium carbonate and calcium 
sulphate. From what is known of the bad effects of the 
heavier petroleum products, such as the mineral oils used for 
lubricating steam-engine cylinders, it appears to be unwise 
to introduce crude petroleum into a steam-boiler. The same 
objection does not apply to refined kerosene, which is not 
known to have any bad effect in a boiler. Both oils are said 
to change the deposits of lime from a hard scale to a friable 
material, which may be easily removed. It is further said that 
these oils will soften and loosen scale already formed. In one 
case 40 gallons of kerosene were used in 24 hours in the 
boilers of a steamer of about 3000 horse-power. These 
boilers showed no incrustation, but considerable corrosion. 

Corrosion is distinguished as general corrosion or wasting, 
pitting, and grooving. 

General corrosion is difficult to detect, as it acts more or 
less uniformly over large surfaces, and even at riveted joints 
the two plates and the rivet-heads waste away equally, so that 
the thinning of the plates is not easily noticed. Old boilers 
not infrequently fail from general corrosion, and then are 



CORROSION AND INCRUSTATION. 95 

likely to fail in the plate rather than in the riveted joint, where 
the double thickness of plate gives an advantage. Boilers 
that have been at work should have the plates below the water- 
line drilled and the thickness measured ; if the effective thick- 
ness of the plate is found to be much reduced, the working 
pressure should be made proportionately lower. Fig. 35 




Fig. 



35- 



shows an example of general corrosion, and Fig. 36 another, 
but complicated with cracking at the rivet -holes. Both show 
the protection given to the plate by the rivet-heads, and one 
may readily see how the wasting of the rivet-heads may be 
overlooked. 

Pitting is likely to occur when the corrosion takes place 
rapidly. It appears to be due to lack of homogeneity of 
the metal of the plate, and sometimes appears to indicate 
galvanic action. Though every precaution to avoid gal- 
vanic action should be taken, it is better to assume damage 
to be due to such action only when there is direct evi- 
dence of its existence. Fig. 37 shows pitting over a large 
surface, and Fig. 38 shows local pitting in the corner of a 
flanged plate with general corrosion of the flat surface of the 
plate. It is fair to assume that the disturbance of the metal 
in the process of flanging may determine the vertical forms 
of the pitting. The horizontal plate shows irregular pitting. 

Grooving is usually due to the combination of springing 
or buckling of a plate and local corrosion. The buckling may 
be due to insufficient staying; then the plate springs back 
and forth as the steam-pressure varies. Or buckling may be 
due to improper staying or fastenings, which localizes the 



9 6 



S TEA M-B OILERS. 




Fig. 37 









ilil 






,ii iiiiiiiii 

arjAte£ -;l" i V 'if ..111 





KIG. .58. 



CORROSION AND INCRUSTATION. 97 

change of shape due to expansion. In either case the metal 
is fretted at the place where the greatest bending takes place, 
and very much weakened. A crack is liable to be formed, 
which may grow wider and deeper till the plate shows signs 
of failure. Such cracks may be very narrow and difficult to 
find, but usually the fretting of the metal, whether a crack is 
formed or not, is accompanied by local corrosion, which 
makes a groove of some width. If the water used forms a 
scale on the boiler-plates, the working of the metal throws 
off the scale and exposes the surface to the water so that cor- 
rosion takes place there, though elsewhere the plate is pro- 
tected. 

As one example of insufficient staying, we may take the 
flattened surface in a wagon-top locomotive-boiler (Plate II), 
where the barrel is expanded to join the shell over the fire- 
box. The surface cannot be stayed from side to side for lack 
of space between the tubes, and is merely stiffened by rivet- 
ing three pieces of T iron to the shell. In this case the T 
irons have through-stays at their upper ends over the tubes. 
Grooving is liable to occur in this locality even when the 
plates are stiffened as shown. 

Grooving from too great rigidity is liable to occur in the 
end-plates of Cornish and Lancashire boilers (see pages 7 and 
8). The long furnace-flues expand more than the external 
shell, and expand more at the top than at the bottom, due to 
the heat of the furnace and of the gases in the flue beyond 
the furnace ; and further, the circulation of water under the 
flues is likely to be imperfect, so that the bottom of the flue 
is not so hot as the top. These unequal expansions must be 
accommodated by the springing of the end-plates, and if the 
springing is too much localized, grooving is sure to occur. 
The furnace-flues should be at least nine inches from the 
shell, and the end-plates should be flanged where they are 
joined to the flues and shell, instead of using angle-irons. 
The use of gusset-plates for staying the ends of these boilers 



9» STEAM-BOILERS. 

is likely to give too much rigidity and to localize the spring- 
ing of the plates, unless care is taken to avoid it. 

Grooving from either too great or too little rigidity can be 
avoided only by a proper design, which must be guided by 
experience. If a boiler shows defects of staying, it may be 
possible to put in additional stays after the boiler is com- 
pleted and at work; or in some cases too great rigidity may 
be remedied by rearranging the staying. Such remodelling 
of a boiler is usually difficult and unsatisfactory. 

Loss from Blowing Out Brine. — In the discussion of 
the use of sea-water in marine boilers, reference was made to 
the custom of feeding one-and-a-half times as much water as 
was evaporated. The feed-water was taken from the hot- 
well of the jet condenser, and was nearly as salt as sea- water,, 
which contains about 1/32 of its weight of salt. The one- 
half excess of water fed was blown out, and carried with it all 
the salt of the entire feed-water; it consequently contained 
3/32 of its weight of salt, and the brine in the boiler had the 
same degree of concentration. 

In calculating the loss from blowing out hot brine it is 
customary to assume that the specific heat of sea-water and 
also of the hot brine is the same as that of fresh water; accu- 
racy in this calculation is not essential. 

For example, find the loss from blowing out hot brine to 
maintain the concentration in the boiler at 3/32, when the 
boiler-pressure is 30 pounds by the gauge and the temperature 
in the hot-well is 140 F. 

The absolute pressure corresponding to 30 pounds by the 
gauge is 44. 7, found by adding the pressure of the atmosphere. 
Since no refinement is needed in this calculation we will use 
instead 45 pounds absolute. A table of the properties of satu- 
rated steam (see Appendix) gives for the heat of the liquid at 
45 pounds absolute, 243.6 thermal units; this is the heat re- 
quired to raise one pound of water from 32 F. to 274°.3 F. v 
that is, to the temperature of steam at the pressure of 45 



CORROSION AND INCRUSTATION. 99 

pounds. The same table gives for the heat required to vapor- 
ize one pound of steam from water at 2j\°.i against a pres- 
sure 01 45 pounds, 922 thermal units. But it is assumed that 
the feed-water has a temperature of 140 F. when taken from 
the hot-well; the corresponding heat of the liquid is 108,2 
thermal units. Consequently, to raise a pound of water from 
140 F. and vaporize it under the pressure of 45 pounds will 
require 

922 -f 243.6 — 108.2 = 1057.4 

thermal units. This is the heat usefully employed. 

Meanwhile for each pound of water vaporized half a pound 
of water is heated from 140 F. to 2/4°.3 F., and then thrown 
away. The heat required to raise half a pound of water from 
140 F. to 274°.3 F. is 

4(243.6— 108.2) = 67.7 

thermal units. This is the heat wasted. 

The total heat applied to forming steam and heating the 
brine blown out is 

1057.4+67.7= 1125.1. 
The per cent of heat wasted is consequently 

^>7-7 
100 X — — L - = 6 per cent. 
1 125. 1 

A considerable portion of the heat lost in the hot brine 
may be transferred to the feed-water drawn from the hot-well 
by the aid of a feed-water heater, and thus saved. A simple 
form of heater may be made by carrying the hot brine 
through a small pipe inside the feed-pipe; the currents of 
water will naturally flow in opposite directions, and thus give 
the most efficient interchange of heat. If the hot-well is near 
the boiler, the feed-pipe may not be long enough to allow of 
this form of heater. 



1 OO S TEA M-B OILERS. 

The density of brine in the boiler is ascertained by a 
salimeter, which is a form of hydrometer graduated to read 
zero in fresh water, 1/32 in sea- water, and the graduation is 
extended to give the density of brine in thirty seconds, so far 
as may be needed. When jet condensers were used at sea it 
was customary to carry the density to 3/32 only. With sur- 
face condensers the density is frequently carried as high as 
6/32 ; no inconvenience is tound in this custom, and as less 
water is taken from the sea the formation of incrustation is 
less rapid. 



CHAPTER V. 
SETTINGS, FURNACES, AND CHIMNEYS. 

The Boiler-setting for a stationary boiler consists of tne 
foundation and so much of the flues and furnace as are ex- 
ternal to the boiler proper. The entire furnace of externally- 
fired boilers is in the setting, and in some cases, as with the 
plain cylindrical boiler, the flues are also formed by the set- 
ting. Some internally-fired boilers — for example, the Lanca- 
shire boiler — have flues in the setting in addition to the boiler- 
flues; others, like the upright boiler (Fig. 6, page n), have 
only a foundation. Locomotive-boilers rest on the frame of 
the locomotive ; they can scarcely be considered to have any 
setting. Marine boilers are seated on plates that are built 
into the framing of the ship. 

Foundations. — The kind of foundation needed depends upon 
the type of boiler to be set and upon the land. With boilers 
of the horizontal multitubular type the weight is distributed by 
the brickwork of the side walls over a considerable length of the 
foundation. With many of the water-tube boilers the load is 
brought to the four corners of the setting. 

On good land a floated concrete bed 2 feet thick extending 
1 foot all around outside of the setting is usually sufficient. 

On made land piling is often necessary. The piles should 
be cut off below water and a concrete footing made over the 
piles. 

The safe bearing loads carried by different kinds of soil are 
generally taken as follows: 



102 



STEAM-BOILERS. 



Good solid natural earth 4 tons per square foot. 

Gravel, well packed and confined, 8 tons per square foot. 

Dry sand, well packed and confined, 4 tons per square foot. 

Dry sand not confined, 2 tons per square foot. 

Marshy soils and quicksands, 1/2 ton per square foot. 

Soft wet clay, 1 ton per square foot. 

Thick beds of clay, 4 tons per square foot. 



I ' I ' I ') I ' FIRE BRICK 



□ 



HARD BRICK 




Fig. 39- 



Concrete for footings may be mixed in the following pro- 
portions: Four bags of Portland cement, three barrows or 
barrels of a clean sharp sand, and five barrows of crushed stone. 
At the end of two weeks this will have set sufficiently hard for 
the work of erecting the boiler to be begun. 

Cylindrical Tubular Boiler-setting. — The setting for a 
pair of cylindrical tubular boilers, like the boiler represented 
on Plate I, is shown by Figs. 39 and 40. The foundation for 
the boiler-setting is a solid bed of concrete 17 feet 8 inches wide, 



SETTINGS, FURNACES, AND CHIMNEYS. 



io 3 



and 21 feet 8 inches long, and 24 inches thick. On firm soil 
the foundation may be conveniently made of large rough-stone 



-21-8- 



j*12= 



" 



_ 



^ 



'* 






-24- 



4K 



© 












i ~i _Lp 







-21-> 



© 







as 



© 



a 



-19-8- 







Fig. 40. 

work, about three feet wide, under the side, middle, and end 
walls only. 



104 STEAM-BOILERS. 

On this foundation there are built the walls that support 
and enclose the boiler and the furnace. The outer walls at 
the sides and rear are double, with an air-space to check the 
conduction of heat. The boilers are each supported by two 
brackets at each end; the front brackets rest on iron plates 
which are built into the side walls; the rear brackets have 
iron rollers interposed to allow for expansion. A brick, 
arch is sprung over the boilers to check the radiation of heat. 
The space between the side and end walls over the boilers 
may be filled with sand, for the same purpose. Coal ashes 
are sometimes used, but they are hygroscopic and liable to 
harbor moisture when the boilers are not working, and should 
not be used. Sometimes the tops of boilers are covered with 
brick and buried in sand; or the sand may be used without 
brick. These methods give ready access to the shell for 
inspection or repairs, but are not so good as a brick arch, as 
water can more readily get to the boiler if it should drip from 
leaky valves or fittings. The rear wall is carried a little 
higher than the top row of fire-tubes, then the space is bridged 
over from the side walls by a horizontal mass of brick-work, 
stiffened and supported by T irons. The smoke-box projects 
over the front wall, and has a rectangular uptake on top, lead- 
ing to a wrought-iron flue which carries the smoke to the 
chimney. 

The furnaces under the front ends of the boilers arc 
enclosed by the side walls, the front wall, and a bridge just 
beyond the first ring of the boiler-shell. The grates rest on 
the front wall and the bridge, as shown in vertical section by 
Fig. 40 and indicated in black on Fig. 39. There is a clear 
space of 24 inches between the grate and the boiler, and a clear 
space of 8 inches over the bridge. The top of the bridge is made 
of fire-brick, and all the walls of the furnaces and other spaces 
that are exposed to the fire are lined with fire-brick. The fifth 
or sixth course of fire-brick above the grate should be laid as 
headers, which serve to support the bricks above, while the brick 









SETTINGS, FURNACES, AND CHIMNEYS. 105 

below the headers are being renewed. All the remainder of the 
brickwork is of hard, well-burned brick. The ash-pit under the 
grate is paved with brick. The floor behind the bridge is covered 
with a layer of sand and paved with brick. 

The side walls are braced by three pairs of buck-slaves, with 
through-rods under the paving and over the tops of the boilers. 

The boiler front is cast iron, with doors opening from the 
furnaces and from the ash-pits. There are also doors opening 
from the smoke-boxes to give access to the tubes. Doors through 
the rear wall give access to the space behind the bridge-wall. 

Between the front tube-sheet and wall in. front of the boiler 
there should be a distance equal to the length of a tube; for it 
may be necessary in a few months to replace one or more tubes. 
Sometimes when there is insufficient room the boiler is placed 
opposite a door or a window. 

The tubes are cleaned from the front, that is to say, the soot 
is blown from the inside of the tubes by a steam-jet taken in 
through the swinging-doors of the front covering the tubes. 

Any number of boilers of this type can be set side by side in 
battery. 

If it is desired to get as much boiler power as is possible in a. 
given space, using this type of boiler, it will be most economical 
to arrange the boilers in two lines with the fronts facing together 
with a distance equal to the length of a tube between the front 
tube-sheets. 

The setting for a tworflue boiler, or for a boiler with several 
large flues in place of the numerous fire-tubes of the tubular 
boiler, is substantially the same as those just described. 

Babcock and Wilcox Water-tube Boiler Setting. — 
This boiler is suspended from a framework built up of I-beams 
with I-beam columns at each corner. The brickwork carries no 
load whatever, the entire load coming to the foundation through 
the columns. 

These boilers may be set with the back wall against the back 
wall of the boiler-house, but it is better to keep at least 3 feet 



io 6 STEAM-BOILERS. 

between the two and to bring the gases out through an opening 
in the back wall rather than to take the gases through the space 
between the two drums. 

By referring to Figs. 13 and 14 it is seen that in order to blow 
the soot from the outside of the tubes three openings are needed 
on the side of the setting. On account of this only two boilers 
can be set together, then there must be a space of from 4 to 5 
feet. 

To make it possible to renew a tube in the boiler there should 
be a distance between the bottom hand-hole in the header and the 
wall equal to the length of a tube, the distance being measured 
in a line parallel with the tubes in the boiler. As a matter of 
fact the hand-holes being elliptical it is possible to get a tube 
in even if this distance measures 3 or 4 inches less than that called 
for by the above. 

Stirling Water-tube Boiler Setting. — This boiler is sus- 
pended in practically the same manner as the Babcock & Wilcox. 
Its tubes are cleaned from the side, and access to the drums is 
from the side, so only two of these boilers can be set together. 

Heine Water-tube Boiler Setting. — This boiler is sup- 
ported at the bottom of the water-legs. The front water-leg 
rests on cast iron columns, built into the brickwork and tied 
together by the casting carrying the fire- and ash-pit doors. The 
rear water-leg is supported by brickwork. Between the brick- 
work and the water-leg, plates and rollers are inserted to allow 
the boiler to expand. 

The tubes in this boiler are cleaned of soot by blowing jets 
of steam through the hollow stays which tie the sides of the water- 
legs together. 

There is a stay in the center of the space between four tubes. 
The tubes are blown in this way from the front and from the 
back. 

Any number of boilers may be set side by side, but there 
must be a space at the back of the boiler-setting. 

The hand-hole covers, covering the openings opposite a tube, 



SETTINGS, FURNACES, AND CHIMNEYS. 107 

are round and can only be removed by dropping them down to 
the bottom of the water-leg where a larger hole is left. 

Marine Water-tube Boiler Settings. — Boilers like the 
Babcock & Wilcox, Thornycroft, Yarrow, and Almy are en- 
closed in a sheet-iron casing lined with blocks of non-conducting 
material. Asbestos, or a compound of which magnesia is a prin- 
ciple ingredient, is commonly used. 

Fire-brick and pumice-stone are used with the Thorny-croft 
boiler to intercept heat that would be radiated downward. The 
spaces in ships under boilers, being more or less inaccessible, 
and being subject to the influence of heat and moisture, are 
liable to show excessive corrosion. 

Furnaces. — There are certain general conditions to which 
the construction of furnaces should conform if high efficiency 
is desired. Some of these depend on the requirements for 
good combustion, and some depend on the size, strength, and 
endurance of the human frame, since hand-firing is almost 
universal. Some of these conditions are violated in the 
design and arrangement of furnaces in certain types of boilers; 
deviation from them involves either a demand for greater 
strength and skill on the part of the fireman, or a loss of effi- 
ciency, or both. 

These conditions, with examples of good and bad practice, 
are as follows : 

There should be an abundant and uniform supply of air to 
the under surface of the grate. About the only cases where 
this condition is not easily fulfilled is in the design of furnace- 
flues of Lancashire boilers and Scotch marine boilers. 

A small supply of air is required over the grate for burn- 
ing smoky fuels like bituminous coal. This air is very com- 
monly supplied through a circular grid or damper in the fire- 
door. The fire-door is commonly protected from direct radi. 
ation by a perforated wrought-iron plate, which also serves 
to distribute the air coming through this grid. Since the 
air thus supplied is cold, it must be small in amount or 



IOS STEAM-BOILERS. 

it will chill the gases and check combustion instead of 
aiding it. 

Leakage of cold air into the furnace, or into the combus- 
tion-chamber or flues beyond the furnace, injures the draught 
and reduces the temperature of the products of combustion, 
and is a direct source of loss. All externally-fired boilers and 
water-tube boilers are liable to suffer from leakage of air. 
Locomotive and Scotch marine boilers are usually free from 
this defect. 

The incandescent fuel on the grate should not come in 
contact with a cold surface. Furnaces lined with fire-brick, 
such as are used for externally-fired boilers, conform to this 
requirement. Vertical boilers, marine boilers, locomotive- 
boilers, and all other boilers having the furnaces in fire-boxes 
or flues, violate this condition, as the plates in contact with the 
fire are kept nearly at the temperature of the water in contact 
with the other side, and are therefore much colder than the 
fire. 

There should be an abundant opportunity for complete 
combustion of gases coming from the fuel with hot air drawn 
through the fuel, before the flame is chilled by contact with 
cold surfaces. This condition is best fulfilled by having a 
clear space over the grate. Externally-fired boilers commonly 
have two feet or more between the grate and the boiler-shell 
immediately over it, and combustion may continue beyond 
the bridge. Locomotive- boilers have from four to six feet 
between the grate and the fire-box crown-sheet, but the flame 
is quickly drawn into and extinguished by the tubes. To aid 
combustion and to protect the lower part of the tube-sheet a 
brick arch is frequently carried across the fire-box, over which 
the flame must pass on the way to the tubes. The lack of 
space over the grate of flue-furnaces, as in the Scotch marine 
boilers, is only partially compensated by the combustion- 
chamber beyond the furnaces. 

Loss from external radiation is almost entirely avoided in 



SETTINGS, FURNACES, AND CHIMNEYS. 109 

internally- fired boilers. Externally-fired boilers are subject 
to more or less loss from conduction and radiation. 

The fire-grate should not be longer nor wider than can be 
conveniently reached by the fireman in throwing on fuel and 
in cleaning the grate. A narrow grate should not be so long 
as a wide grate. In general, a hand-fired grate should not be 
more than six feet long, and if it is over four feet wide two 
fire-doors should be provided. These conditions are usually 
fulfilled by the design of externally-fired boilers, locomotive- 
boilers, and water-tube boilers. Attention has been called 
already to the difficulty of getting proper space for the grates 
in flue-furnaces. With the common diameters of the furnace- 
flues a length of five feet should not be exceeded. Flues in 
marine boilers have been made eight feet long; in such case 
the further end of the grate is sure to be inefficiently fired. 
To aid in firing, and to use the space below and above the 
grate to the best advantage for the supply of air and for 
combustion, the grate is commonly given an inclination down- 
wards of about 3/4 of an inch to the foot. 

As an extreme example of deviation from these propor- 
tions we may cite the Wooten locomotive fire-box, designed 
to burn anthracite slack. The grate is made about eight feet 
wide and twelve feet long. 

For convenience in throwing on coal and in cleaning the 
grates, the floor on which the fireman stands should be about 
two feet below the grate. This can usually be arranged for 
stationary boilers. The grate of a locomotive is commonly 
below the floor of the cab ; this facilitates throwing on the 
coal ; some form of rocking grate is used to shake down the 
ashes. The side furnaces of Scotch marine boilers are com- 
monly too high for convenient firing, and the middle furnaces 
may be too low for convenience in cleaning the grate. 

Excessive heat in the fire-room should be avoided as far as 
possible; the labor of feeding and cleaning a furnace for rapid 
combustion is always severe, and when combined with great 



HO STEAM-BOILERS. 

heat it soon exhausts the fireman. If land boilers are 
properly clothed to avoid radiation, and if the fire-room is 
airy and well ventilated, the heat will not be excessive. It is, 
however, very difficult to avoid excessive heat in the stoke- 
hole of a steamship. Of course the radiation from the glow- 
ing fuel when the fire-doors are open cannot be avoided, but 
it ought to be possible to clothe the fronts of marine boilers 
more perfectly than is now the common practice. Moreover, 
the ventilation of the stoke-hole is commonly defective ; the 
air pours down through the ventilators and makes cold spots 
immediately beneath them, while other parts of the stoke- 
hole are hot. Forced draught with closed stoke hole usually 
gives good ventilation ; with closed ash-pit it is liable to give 
defective ventilation. 

In certain types of water-tube boiler there is not sufficient 
space over the fire to enable the gases to mix. If the unmixed 
gases are chilled by coming in contact with the cold tubes in- 
complete combustion results. Analyses of furnace-gas samples 
taken at different parts of the gas passage often show CO and 
an excess of O. This shows that the gases were not mixed till 
the second or third gas passage was reached, where the tem- 
perature was too low for the CO to burn. 

The Dutch oven-furnace, previously referred to in the dis- 
cussion of independently-fired superheaters, has been applied 
to these boilers and has helped somewhat. By raising the boiler 
up and using the Dutch oven-furnace, as shown by Fig. 41, the 
gases may be made to travel 9 or 10 feet before coming in con- 
tact with the tubes. 

This setting gives very nearly complete combustion and is 
very efficient as a smoke-consuming device. 

A relieving arch in either side wall carries the fire-bricks 
above the arch and makes it possible to renew the fire-brick 
adjacent to the fire without disturbing the bricks above. 

Great care should be taken in laying the fire-bricks in a 
furnace of this sort. The bricks should be laid with as thin a 



SETTINGS, FURNACES, AND CHIMNEYS, m 








112 STEAM-BOILERS. 

layer of clay between them as will serve to give a uniform bear- 
ing. 

Fire-bricks which have been exposed to the weather during a 
storm or fire-bricks which have been left out in winter weather, 
will crumble as soon as they are heated in a furnace. 

But few masons seem to be aware of this fact. 

Grate-bars are commonly made of cast iron, as it is 
cheaper and lasts as well as wrought iron. Sometimes wrought- 
iron bars are used on locomotives and elsewhere, if they are 
expected to withstand rough usage. 

Cast-iron fire-bars are generally 5/8 to one inch thick at the 
top, and 5/16 to 5/8 of an inch thick at the bottom; they are 
about two inches deep at the ends, and three to five inches deep 
at the middle. To provide for wasting of the upper surface, 
they are made full width for some distance down from the top, 
thus forming a sort of head; then they are rapidly narrowed 
down to a web that is tapered gradually toward the bottom. 
The space between the bars depends on the draught and the 
nature of the fuel; with ordinary coal and natural draught 3/8 
to 1/2 of an inch is allowed. Lugs or projections are cast at the 
ends and at the middle, so that the bars shall be properly spaced 
when laid side by side. With forced draught the bars may be 
3/8 to 9/16 of an inch wide at the top, and the distance between 
the bars may be 1/16 to 1/4 of an inch. The area of the air- 
spaces through the grate-bars is ordinarily from 30 to 50 per 
cent of the area of the grate; if shavings are to be burned, a much 
greater air-space is needed and a grate, like Fig. 43, is often used. 
The combined area of the holes may be made as great as the 
projected area of the bar, thus giving 100 per cent air-space. 
A dead-plate two inches wide should be fitted to the furnace- 
tube of marine boilers to prevent admission of air at that place. 

The length of fire-bars should not exceed four feet; the 
length of a fire-grate may be made up of two or three short bars. 
Bars are commonly cast in pairs, or three or four may be cast 
together, to resist twisting and warping under heat. 



SETTINGS, FURNACES, AXD CHIMNEYS. 



IJ 3 



The usual form of grate-bar cast in pairs with lugs at the side 
is shown by Fig. 42a. 

The herring-bone grate is shown by Fig. 426; a grate used 
for sawdust, shavings or other inflammable material of this sort 




Fig. 42a. 




Fig. 426. 

is shown by Fig. 43. Fig. 44 shows a form of grate designed by 
Prof. Schwamb for burning screenings at a high rate of com- 
bustion. The construction of the grate is shown by the section. 
A boss around each air opening allows ash to collect in the small 




Fig. 43- 



recesses between the air openings on the top of the grate. This 
ash prevents clinkers from adhering to the bars. Bars of this 
sort have been used twenty-four hours a day for over two years 
under boilers forced 80 per cent over rating without trouble. 

Wrought-iron fire-bars are formed with a head and web, 
but are of uniform depth, as they are cut from a rolled bar; they 
are bolted together in Lets of six, with washers to give the proper 



ii4 



STEAM-BOILERS. 



spacing. For marine boilers they may be 5/16 of an inch thick 
at the top, with spaces 3/16 of an inch wide, or less. 




Fig. 44. 

Rocking Grates. — The labor of breaking up the clinker 
which forms on grate-bars is very much reduced by employing 
some form of rocking grate. On locomotives, where the rate of 
combustion is hi^h and where the fire should always be in good 
condition, some form of rocking grate is considered essential 
in American practice. 

In Fig. 45 A and B represent alternate grate-bars which 
are supported at semicircular notches at the ends. CO is a 




b' a 






r^-- 




Fig. 45. 



cast-iron crank-shaft extending across the furnace at one 
end of the grate-bars. Shallow bars like A rest on cranks 
that are above the line CO, and deep bars like B rest on 



SETTIXGS, FURNACES, AXD CHIMXEYS. T15 

cranks below that line, as shown at a, a' , and a" , and at b 
and b' '. The further ends of the grate-bars rest on another 
crank-shaft like CO ' . At the lower right-hand corner of the 
figure c" represents the end of the crank-shaft and d repre- 
sents an upper crank carrying a shallow bar like A. At g is 
a head to which a lever may be applied to rock the crank- 
shaft. When the crank-shaft is rocked the alternate bars are 
thrown back and forth, and grind up the clinker so that it 
falls through the grate into the ash-pit. 

Firing. — Care, skill, and intelligence are required to burn 
coal rapidly and economically. There is a marked difference 
in the ability of trained firemen to make steam with a given 
boiler, and probably there is nothing more wasteful and costly 
than a poor or careless fireman. 

The method to be adopted in firing depends on the type 
of boiler, the kind of coal, and the rate of combustion. Three 
methods of firing may be distinguished : 

Spreading, which consists in distributing small charges of 
coal evenly over the surface of the fire at short intervals. In 
this method the object is to deliver the coal just where it is 
wanted, and then not disturb it. The fire can then be kept 
in just the right condition at all times, and probably the best 
results can be thus obtained, both in absolute quantity of 
steam and in economy, provided the coal used is well adapted 
to this method. Care must be taken to have the door open 
as little as possible, or an undue amount of cold air will be 
admitted through the fire-door. 

Anthracite coal should always be fired by spreading, and 
should be disturbed as little as possible after it is thrown in 
place. Unless the fire is urged, very little clinker will be 
formed, and the ashes are readily shaken out by a pick or 
hook run up between the fire-bars. The thickness of the fire 
may vary from four to twelve inches, depending on the size of 
the coal and the strength of the fire. 

Dry bituminous coal, and other bituminous coals, if not 



u6 



STEAM-BOILERS. 



very smoky and if in small pieces, can be advantageously fired 
in this way. Each shovelful thrown on will give off volatile 
matter, which will burn with the excess of air coming through 
the fuel, and very little smoke will result. 

Side firing consists in covering all of one side of the fire 
with fresh fuel, leaving the other bright. The smoke given 
off from the fresh fuel can then be burned with the hot air 
coming through the bright fire. This method of firing is best 
carried on with two furnaces leading to a common combus- 
tion-chamber; the furnaces are fired alternately, at regular 
intervals, with moderate charges of coal. It is customary to 
admit air through the grid in the fire-door when the fuel is 
giving off gas. 

Coking the coal on a dead-plate, or on the grate just inside 
the fire-door, is perhaps the best way of burning a smoky 
coal. The volatile products driven off from the heap of coal 
near the furnace-door burn with the hot air, coming through 
the clear fire at the rear. As soon as the charge is coked it 
is pushed back and spread over the grate, and a new charge 
is thrown on. 

With bituminous coal the fire should be thicker than with 
anthracite coal; from 6 to 16 inches gives good results. 

The method too often followed by ignorant and indolent 
firemen, of throwing on as much coal as the furnace will hold 
and then sitting down to wait till the steam-pressure falls, 
needs to be mentioned only to condemn it. 

Mechanical Stokers, feeding coal regularly from a 
hopper, have been invented in a variety of forms from time 
to time. Since the hopper may be made of considerable 
size, manual handling of the coal may be entirely avoided, 
and one man can easily attend to a number of furnaces with 
little labor and exposure to heat. It would appear also that 
a more even and better- regulated combustion may be had 
than with hand-firing. The primary object, however, is to save 
labor and it is foolish to install a mechanical stoker in a plant, 



SETTINGS, FURNACES, AXD CHIMNEYS. 117 

unless a saving can be made in the cost of labor or the capacity 
of the plant increased. There are many plants equipped with 
mechanical stokers where the hoppers are filled by the shovel. 
Often it is harder to shovel the coal into the hoppers of the stoker 
than it would be to threw the coal on to the grate, and as many 
firemen are needed as would be required to fire the boiler by 
hand. 

AYith some mechanical stokers working under forced draught 
the capacity of the plant may be increased considerably above 
what could be obtained by hand firing, but, in general, it does 
not pay to use stokers in plants of less than 1500 boiler horse- 
power, as the saving in labor is not great enough to pay for the 
necessary repairs and the interest on the first cost of the stokers. 

The Roney Stoker. — The Roney stoker, shown by Fig. 46, 
as applied to a B. & W. water-tube boiler, may be taken as an 
illustration of a mechanical stoker. The grate-bars extend across 
the furnace and form a series of steps down which the fuel slides, 
burning on the way down. Each grate-bar is hung on pivots 
at the ends, near the top, and has a rounded lug at the bottom 
that rests in a groove in a rocker-bar, as shown by Fig. 47. 

The rocker-bar has a slow and regular reciprocation de- 
rived from a small steam-engine, which tips the grate-bars so 
that the upper surfaces are inclined downward to make the 
fuel slide, and then rights them to check the motion of the 
fuel. The coal from the hopper falls onto a horizontal plate, 
from which it is pushed forward by a " pusher " that is driven 
by the steam-engine which drives the rocker-bar. The rate 
of feeding the fuel can be controlled by changing the stroke 
of the pusher, and by regulating the number of strokes of the 
pusher and of the rocker-bar per minute. The ashes, clinker, 
and other unburned refuse collect on a dumping-grate at the 
foot of the grate-bars. This grate is shown in normal position 
by heavy lines in Fig. 47, and in the dumping position by 
light lines. 

This grate appears to be well adapted to burn smoky fuel, 



n8 



STEAM-BOILERS. 




Floor Line 



Fig. 46 




Fig. 47- 



SETTINGS, FURNACES, AND CHIMNEYS. 119 

as such fuel is well coked at the top of the grate, and the volatile 
parts driven off by coking can burn with the excess of air coming 
through the grate at the bottom. 

If the rate of feed is too fast, it is evident that unburned 
coal will work down onto the dumping- grate, and will appear 
in the ashes. If the rate of fuel is regulated so that no coal 
appears in the ashes, the fire becomes thin at the bottom, and 
an excess of air is liable to enter there ; certain tests on this 
grate have indicated such an excess of air, \thich is the side 
on which the fireman is liable to err, as he may not know 
how much waste he thus occasions, while he can see the coal 
in the ashes. 

The American Stoker. — This stoker applied to a hori- 
zontal multitubular boiler is shown by Fig. 48. The grate ordi- 
narily used with the boiler is replaced by a shallow iron trough, 
extending nearly to the bridge-wall. The trough is not over 
one third of the width of the regular grate. Fire-brick are laid 
either side of the trough, thus blocking off the grate. Air from 
a blower is sent into the furnace through tuyer-blocks located 
near the top of the trough. 

The jets of air issuing from these openings are inclined up- 
wards by a trifling amount. 

Coal is fed from the hopper to a worm rotated at a very slow 
speed by a steam cylinder. 

The coal pushed along by the worm rises through the trough 
and makes a mound which gradually extends on to the brick 
either side of the trough. 

The fire is hottest at the surface of the mound opposite the 
tuyers. Any carbon or volatile gases driven off from the green 
coal as it rises through the trough are completely consumed in 
their passage through the hot outer layers. 

Both this stoker and the one shown by Fig. 49 increase the 
capacity of a boiler. Many people do not realize that a boiler 
forced beyond its capacity will not last as long as it would if run 
at normal rating. These stokers are good smoke-consumers. 



120 



STEAM-BOILERS. 



The ashes and clinkers have to be removed through the fire- 



door; 




Fig. 49 



Any stokers to which air is admitted in this way, if improperly 
handled, may give a blowpipe effect. This is due to the air 
escaping through the coal in one spot instead of being distributed 
through the entire mass of coal. 



SETTINGS, FURNACES, AND CHIMNEYS. 



121 




122 STEAM BOILERS. 

The heat generated by this action is localized and very in- 
tense. 

The Jones Under-fed Stoker.— This stoker, shown by 
Pig. 49, is similar in its action to the American. Air is forced 
into the ash-pit in this case. Coal is forced in intermittently by 
-a steam piston. This piston may be operated by a hand-lever, 
'or it may be timed to operate as many times an hour as the 
timing device is set for. 

The Green Traveling Link-grate. — Chain grates have 
been used to a considerable extent with the poorer grades of 
soft coal. Fig. 50 illustrates the Green traveling grate applied 
to a Heine boiler. 

Power from a shaft overhead oscillates the vertical rod at the 
left of the cut. A ratchet carried by the arm moved by this rod 
gives motion to a train of gears. The link-grate is moved by 
; sprocket-wheels keyed to the shaft at the extreme left of the 
figure. The entire grate and frame may be withdrawn from the 
furnace. 

Smoke Prevention has become a matter of great social 
importance in cities where much smoky coal is used. Though 
the loss through imperfect combustion of carbon to the form 
of carbon monoxide may be great, and though there may be 
an appreciable loss if the volatile parts of coal are driven off 
unconsumed, it is a fact that the loss in smoke, even when it 
is dense and black, is not enough to induce coal users to take 
the trouble to prevent the formation of smoke. Not infre- 
quently it has been found that the methods used to prevent 
smoke are accompanied by a loss instead of a gain. For ex- 
ample, smoke burning by the alternate firing of two furnaces, 
leading to a common combustion-chamber, may give a slightly 
greater efficiency if just enough hot air in excess is admitted 
through the clear fire, to burn the gases distilled from the fresh 
charge. If the clear fire must be kept too thin, and thus 
admit a large amount of air, in order that the smoke may be 
burned, there will be a loss of efficiency. Though it is not 



SETTINGS, FURNACES, AND CHIMNEYS. 123 

well proved, it is asserted that the mixture of finely divided 
carbon, in the form of smoke, with carbon dioxide may give a 
clear gas with the formation of carbon monoxide, and thus with 
a notable loss. The same difficulties arise when side firing 
and coking are resorted to with smoky fuels. 

One of the most perfect arrangements for smoke prevention 
which has yet been tried, consisted of a detached furnace with 
small grate-area and a deficient air-supply, so that the coal was 
distilled and burned to carbon monoxide ; the resulting hot 
gases were then burned under a steam-boiler. The method 
was suggested by the producer-furnaces used for making gas for 
the open-hearth process of steel-making. The objections are 
the loss of heat by radiation from the detached furnace and the 
space occupied by that furnace. Though reported to be a 
success so far as the prevention of smoke was concerned, it 
does not meet with approval. 

It is a common experience, that when laws against making 
smoke are enforced, users of fuel have chosen to buy anthra- 
cite coal or coke, or in some cases have used crude petroleum 
oil. 

Down-draught Furnaces. — In connection with the sub- 
ject of smoke prevention, attention should be called to down- 
draught furnaces, which have the connection with the chimney 
below the grate. The supply of air is through the fire-door 
to the top of the fire, which has a very attractive appearance, 
as it burns brightly at the upper surface unless obscured by 
fresh fuel. A natural inference is, that the combustion is per- 
fect in a down-draught furnace, and that it should give a not- 
able gain in economy of fuel, but a little consideration shows 
that such a furnace is subject to the same conditions as an ordi- 
nary furnace. If there is either an excess or a deficiency of air, 
the combustion will be imperfect; in the latter case, as with an 
ordinary furnace, smoke may appear at the top of the chimney. 
Tests made on a boiler using first an ordinary and then a down- 



124 



STEAM-BOILERS. 



draught grate have commonly shown little if any advant 
favor of the latter. 

Down draught furnaces, if properly arranged and fired, can 
be made to burn inferior fuels which have a large amount of 
volatile matter without making much smoke; this may be a 
matter of great importance in cities where laws against smoke are 
enforced. 

Hawley Down-draught Furnace. —This furnace consists 
of a water-grate, an ordinary grate beneath the water-grate, and 
an ash-pit beneath this. There are three sets of doors. 

The upper doors are kept open nearly all of the time. Coal 
is fired through the upper doors. The coal next to and in con- 
tact with the water-grate is the hottest,, and any volatile products 
driven off from the green coal have to pass downward through 
the water-grate and over the fire on the lower grate before escap- 
ing into the space beyond the bridge-wall. 

The lower grate is supplied with coal which drops through 
the water-grate when the slice-bar is used. This fire is what 
would be called a dirty fire and shows clinkers and ash. 

As a general rule firemen are not apt to keep a sufficient 
depth of fire on this lower grate. A fire about 6 inches thick 
seems to give best results. 

The water- grate adds a large amount of very efficient heating - 
surface to a boiler, and in consequence increases the capacity of 
the boiler without reducing the economy. 

Oil-burning Furnaces have the oil thrown in by sprayers 
or atomizers, and the oil burns in a flame that is about four 
inches in diameter and two to four feet long. The sprayer 
has two conical converging tubes, one inside the other, some- 
thing like the steam and water nozzles of a steam-injector. 
Compressed air or superheated steam is supplied to the inner 
tube, and the oil is drawn through the outer tube and thrown 
into fine spray mingled with air. Compressed air is the 
better, considering proper combustion only, but the great 
convenience of using steam near a steam-boiler has led to its 



SETTINGS, FURNACES, AND CHIMNEYS. 125 

common use. The proportions of air and oil may be nicely 
regulated, so that perfect combustion may be secured without 
smoke. 

In the United States oil has been used for fuel at or near oil- 
fields, or in cities where laws against smoke are enforced. 

The use of oil for fuel on war-ships has received favorable 
consideration from some authorities, the evident advantages 
being the great calorific power of oil and the ease with which 
the fires may be maintained and regulated. The fact that oil 
in tanks may be set on fire by explosive shells has prevented 
any extensive adoption of oil for fuel on war-ships. 

Oil for fuel should be stored in tanks outside the fire-room, 
and if possible the tanks should be lower than the burners. 
The oil is pumped from the tank to the burners as required. 
This is to avoid accidental flooding of the furnace and the fire- 
room with oil, and the attendant danger of conflagration. 
Crude oil is more dangerous than refuse oil, since the former 
contains all the volatile components that vaporize at ordinary 
temperatures and form explosive mixtures with air. 

Induced Draught and Forced Draught. — When a higher 
rate of combustion is required than can be had with natural 
draught, resort is had to forced draught, by aid of which 150 
pounds of coal can be burned per square foot of grate-surface 
per hour. 

Three systems of forced draught are in common use, 
namely, with a closed stoke-hole, with closed ash-pits, and in- 
duced draught. 

Induced draught has long been used on locomotives, by 
the action of the exhaust-steam thrown through the smoke- 
stack. The same method is used to some extent on tug- 
boats. This method is simple and effective, but can be used 
only with non-condensing engines. Induced draught may be 
obtained by a centrifugal, or other form of blower, in the 
chimney. It is essential that an economizer should be used 
to cool the gases before they come to the blower. 



126 STEAM-BOILERS. 

On steamships forced draught has been obtained by the 
aid of centrifugal fan-blowers. The method with closed ash- 
pit has been used with success on merchant steamers and 
some war-ships. With this method air drawn from the fire- 
room passes through a blower and is delivered to the ash- 
pit, which has an air-tight door. If the pressure in the ash- 
pit exceeds the resistance to the passage of air through the 
fuel, flame comes out around the fire-door unless it is also 
made air-tight. When the fire-door is opened to throw on coal 
the blast must be shut off from that furnace and all others 
having a common combustion-chamber, or flame will shoot 
out into the fire-room in a dangerous manner. One reason 
why it has not been used on war-ships is the difficulty of 
properly ventilating the many small fire-rooms in which boil- 
ers are placed. 

The closed stoke-hole has been the customary way of get- 
ting a forced draught on torpedo-boats and on other naval 
vessels. The stoke-hole is closed air-tight, admission and 
egress being through air-locks, and air from without is forced 
in through a centrifugal blower till the pressure exceeds that 
of the atmosphere. When a fire-door is opened to attend to 
the fire, there is a strong inrush of air that is liable to make 
the tube-plates leak. So great difficulty has been experienced 
from this cause, when forced draught has been used with the 
Scotch boiler, that many naval officers doubt its advisability 
for large ships. The success of forced draught on the loco- 
motive and on torpedo-boats with modified locomotive-boilers 
may be attributed partly to the type of the boiler and partly 
to the fact that there is only one boiler and one furnace. 
When two boilers are used on a torpedo-boat, each has its 
own chimney. 

On locomotives the induced draught is frequently equiva- 
lent to a column of water five or seven inches high. Forced 
draught on torpedo-boats has approached those figures, but is 
usually less. Large ships usually have the forced draught re- 



SETTINGS, FURNACES, AND CHIMNEYS. 1 27 

stricted to two inches of water. On account of the resistance 
to the entrance of air to the fire-rooms of war-ships, through 
ventilating shafts, gratings, etc., it has been common to assist 
the draught by running the blowers without closing the air- 
locks. 

The increased cost of coal has led many to burn screenings or 
buckwheat coal by means of a forced draught. 

A blower driven by a steam-engine supplies air to the ash-pit 
at from 1/2 to 4 inches water pressure. A rapid rate of com- 
bustion is maintained, and even though the cheap coal is not 
burned as economically as it might be, still the poorer coal at 
the present prices shows a saving in the cost of making steam. 

The speed of the engine driving the blower is controlled by 
the pressure in the boiler, a damper regulator operating the 
throttle of the engine. When the damper regulator has closed 
the throttle, the engine is kept turning fast enough to pass the 
dead-centers by steam, admitted through a small pipe with valve, 
which by-passes the throttle controlled by steam pressure. 

In the induced draught system, as arranged in large plants, 
the gases are drawn from the grate through an economizer into 
the exhaust-fan, which then discharges the gases at about 300 F. 
into the stack. The stack serves simply to carry the gases away. 

Howdens System. — The temperature of gases in the up- 
takes of marine boilers is frequently high, especially when forced 
draught is used. In Howden's system the products of com- 
bustion pass through vertical transverse tubes placed in an en- 
largement of the uptake. Air to supply the fire is forced over 
these tubes by a fan-blower and is thereby warmed, thus saving 
heat and giving quicker combustion. Care must be taken in 
using this system not to go too far, or the fire may become too hot 
and rapidly burn out the fire-grates and do other injury. 

Fire Cracks. — Fire cracks are often found on old boilers 
at the joints exposed to the fire. The two rivets at the left in 
Fig. 51 show such cracks. 

These cracks are caused by the repeated buckling, between 



128 



STEAM-BOILERS. 



the rivets, of the plate exposed to the fire. This plate becomes 
much hotter than the plate back of it which is in contact with 
the water in the boiler, and any change in the temperature of the 
fire is felt by the plate. 

Innumerable repetitions of this action ultimately starts a 
crack which extends as shown. If a crack extends beyond a 
rivet it should be plugged to prevent the crack from extending 
to the edge of the lap of the other plate. This plug is a piece of 
soft copper driven into a hole drilled about 3/8 inch diameter. 

The cracks are most always at the rivets, but sometimes a 
crack will be found between two rivets. 




Fig. 51. 

In case a fire crack should leak much the leak may be stopped 
for a time by countersinking the plate, as shown by the right- 
hand rivet and driving in a very soft rivet. The metal of the 
rivet will flow out into the crack. 

Cleaning Fires. — Three tools are used in clearing the 
grate: they are a long straight bar known as the slice-bar, a 
similar bar with the point bent at right angles to make a hook, 
and a long-handled rake with three or four prongs. The hook 
may be run along between the grate-bars from below, to clear 
the spaces from ashes and clinker. The slice-bar is thrust under 
the fire on top of the grate to break up the cinder; it is used also 
to stir and break up caking coals. The rake is used to haul 
the fire forward or to draw out cinder. 



SETTINGS, FURNACES, AND CHIMNEYS. 129 

To clean a fire the fireman breaks up the cinder with the 
slice-bar and rattles down the ashes; if necessary, he works the 
fire back toward the bridge and exposes the grate in front, which 
may then be thoroughly cleaned. Then he hauls the fire forward 
and cleans the back end of the furnace. Cinder which will not 
break up and pass through the grate is pulled out through the 
fire-door. Some firemen prefer to clean the grate one side at a 
time. After the grate is cleaned the fuel left is spread evenly over 
the grate and fresh fuel is thrown on. The fire should be allowed 
to burn down before cleaning, but a fair amount of glowing 
coal should be left to start a new fire briskly. Before beginning 
to clean the fire the draught should be checked by closing dampers 
or otherwise. 

Economizers. — An economizer consists of a series of ver- 
tical cast-iron tubes placed in the flue of a boiler between the 
boiler and the stack and used to heat the feed-water with heat 
recovered from the flue-gases. 

Any heat taken up in this way is just so much heat gained, 
provided the draught is not so reduced by the extra resistance 
offered to the passage of the flue-gas as to lessen the capacity of 
the boiler. 

An economizer will show a greater saving on a plant which is 
forced than on a plant which is running at a moderate rate. 
Ordinarily a saving of from 8 to 10 per cent will be made. It is 
not advisable, however, to install economizers on small plants. 

Soot is removed from the outside of the tubes by scrapers in 
the shape of rings which are drawn over the tubes by power. 

There must be two flues: one through the economizer con- 
necting with the chimney and one leading directly from the boiler 
to the chimney. 

Suitable dampers are located so as to send the gases through 
either flue. This makes it possible to repair the economizer 
while the boilers are running. 

The heat taken up by the economizers of large boiler-plants 
may be the equivalent of four or five hundred horse-power. 



SETTINGS, FURNACES, AND CHIMNEYS. 



J 3i 




CROSS SECTION 



Fig. 53. 



132 



STEAM-BOILERS. 



Should the economizer be disabled the power of the boilers 
would be reduced by this amount. This has led to the use of 
what are known as unit economizers, small economizers, one for 
each boiler or for each battery of two boilers. 

Feed-water enters the economizer at the end nearest the 
chimney and leaves at the end nearest the boiler where the gases 
are hottest. The feed-water is generally pumped through the 
economizer directly to the boiler, thus putting the economizer 
under boiler pressure. In some instances, city water under 40 
pounds pressure is taken through the economizer into the pump. 
The tubes are generally 4 inches inside diameter and about 
9 feet long. They are arranged in groups. 

It is customary to leave a space 9 inches wide on each side 
between the tubes and the brickwork on large economizers and 
on one side on small economizers to enable a man to inspect the 
tubes. These passages are closed by dampers. 

From 4 to 5 square feet of heating-surface are allowed per 
boiler horse-power in most cases. Economizers are made by the 
Green Fuel Economizer Co., and by the B. F. Sturtevant Co. 
Figs. 52 and 53 show two different arrangements of the Green 
economizer. 

Chimneys. — There are a number of different kinds of chim- 
neys in use to-day, the red-brick stack, the radial brick stack, 
the self-supporting steel stack, the guyed steel stack, and concrete 
chimneys. 

The steel chimneys are sometimes lined with fire-brick and 
sometimes unlined. 

The life of a steel chimney depends upon the care taken of 
it; probably ten to twelve years is a fair estimate of the life of 
such a chimney. A steel chimney deteriorates much more rapidly 
when idle than when in use. A brick stack lasts a great many 
years. 

Radial brick chimneys are made of a special brick, much 
larger and thicker than the ordinary red brick, shaped to the 
curve of the chimney on two faces and radial on two faces. 






SETTINGS, FURNACES, AND CHIMNEYS. 



J 33 



There are five or six holes about i inch square running ver- 
tically through these bricks. 

Radial brick chimneys are very numerous in Germany. 
Many are being built now in this country. They are known 
here as the Custodis, the Heinicke, and the Kellogg chimneys. 

Concrete reinforced by iron bars has been used for chimneys 
during the last few years. It has not always proved to be a 
success, in some cases, because of faulty design, in others, because 
of poor material and poor construction. 

Various formulae have been proposed for use in finding the 
diameter and the height of a chimney needed for a given power* 
those given by Kent, by Christie, and by Gale being best known. 

The following table, figured by William Kent from his formula, 
is borne out by practice. The table is figured on the assumption 
that 5 pounds of coal are required per boiler horse-power. If 
less coal is required the capacity of the chimney is increased, and 

SIZES OF CHIMNEYS WITH APPROPRIATE HORSE-POWER OF 

BOILERS. 



Diam- 


Height of Chimneys and Commercial Horse-power. 


Side 
Sq're. 
Inches 


Acl 


ua! 


eter in 
Inches. 


50 
Ft, 


60 

Ft, 


Feet. 


80 
Feet. 


90 
Feet. 


100 
Feet. 


no 
Feet. 


1 
Feet 


; 1 =;o 
Feet 


175 
Feet 


200 
Feet 


Square 
Feer. 


iS 


23 

49 

65 
84 

'. '■ 


25 
38 
54 
72 
92 
115 
141 


27 

41 

58 

78 

100 

125 

152 

183 

216 


















16 
19 
22 
24 
27 
30 
32 
35 
38 
43 
48 
54 
59 
64 
70 
7 5 
80 
86 
90 
96 
ior 
106 

IT2 
II 7 
122 
127 


2 

3 

3 

4 

5 

7 

8 

9 

12 

z 5 

19 

23 

28 

33 

38 

44 

50 

56. 

63. 

70. 

78. 

86. 

9 5 . 

I0 3- 

113. 


■77 
.41 
• 14 
.98 
.91 
94 
07 

30 

62 

57 
90 
64 
76 
27 
18 
48 
18 
27 
75 
62 
88 
54 
59 
°3 
86 
10 


24 

27 

3° 

3 3 

36 

39 

42 

43 

54 

60 

66 

72 

78 

84 

00 

96 

102 

108 

114 

:2o 

126 

132 

138 

144 


62 
83 

107 

133 
163 
196 
231 
311 
363 
505 


IT 3 
141 
173 
208 
245 
33° 
427 
536 
658 
792 


'182 

219 

258 

348 

449 

565 

694 

835 

995 

1163 

1344 

1537 


271 

365 

472 

593 

728 

876 

1038 

1214 

1415 

1616 


'389 

503 

632 

776 

934 

1107 

1294 

1496 

1720 

1946 

2192 

2459 


55i 
692 
849 
1032 
1212 
1418 
1639 
1876 

2133 
2402 
2687 
2090 
3308 
3642 
399i 
4357 


'748 
918 
1105 
1310 
1531 
1770 
2027 
2303 
2 594 
2903 
3230 
3573 
3935 
43ii 
4707 


'981 
1181 
1400 
1637 
1893 
2167 
2462 
2773 
3003 
345 2 
3820 
4205 
4605 
5031 



134 STEAM-BOILERS. 

its new rating may be obtained by multiplying the figure given 
in the table by 5 and dividing by the actual coal used per boiler 
horse-power. 

Chimney Draught.— The draught produced by a chimney 
is due to the fact that the gases inside the chimney are hotter 
and consequently lighter than the outside air. Though these 
gases at a given temperature and pressure have a little greater 
specific gravity than air at the same temperature and pressure, 
the difference is not much, and may be neglected in the dis- 
cussion of chimney draught. 

To get an idea of the production of draught by a chimney, 
we may consider the conditions that would exist if a chimney 
were filled with hot air and closed at the bottom by a horizon- 
tal partition or diaphragm. The pressure of the air at the top 
of the chimney, due to the atmosphere above that level, is the 
same on the gases inside the chimney and the air outside. The 
pressure on the diaphragm at the bottom is the sum of the 
pressure ,at the top of the chimney and of the pressure due to 
the column of hot air in the chimney. At the under side of 
the diaphragm the pressure will be that at the top of the 
chimney plus the pressure due to a column of cold air as high 
as the chimney. This difference of pressure is considered to 
be the draught, in all theories of the chimney. It may be 
readily calculated for an assumed set of conditions. For an 
actual chimney the draught or difference of pressure inside 
and outside the chimney may be shown by a U tube partially 
filled with water, and having one end connected to the inside 
of the chimney and the other open to the air. The water 
rises in the leg connected with the inside of the chimney ; the 
difference of level measures the draught. 

Suppose now that a small hole is opened in the dia- 
phragm at the bottom of the chimney : cold air from without, 
under the greater pressure existing there, will enter and will 
force some of the hot air out at the top of the chimney. If the 
air is heated as it enters, to the temperature in the chimney, 



SETTINGS, FURNACES, AND CHIMNEYS. 135 

we shall have a continuous flow of cold air into and of hot air 
out of the chimney. Replacing the diaphragm by a grate 
charged with burning fuel, through which cold air enters and 
burns with the fuel, we have the actual conditions of chimney 
draught. 

For an example, we will calculate the difference of pres- 
sures, or draught, if a chimney 100 feet high is filled with air 
(or gas) at 500 F., while the temperature outside is 60 ° F. 

The weight of a cubic foot of air at 32 F. and at the 
average pressure of the atmosphere (14.7 pounds) is about 
0.0807 of a pound. Now the weight of air at a given pressure 
is inversely proportional to the absolute temperature, that is, 
to a temperature obtained by adding 459°.5' to the temperature 
given by a Fahrenheit thermometer. Consequently we have 
for the weights of a cubic foot of hot gas and of a cubic foot 
of cold air: 

Hot gas, O.0807 X 459 ' 5 , 32 =00386; 
459-5 + 5oo d 

Cold air. 0.0807 X 459 ' 5+ ^ 2 =0.0764. 
459.5 + 60 

A column of hot gas 100 feet high* and 1 foot square will 
weigh t,.86 pounds, and would give that pressure in pounds 
per square foot on a diaphragm at the bottom of the chimney. 
The cold air outside will give a pressure of 7.64 pounds per 
square foot. The difference of pressure or draught will be 

7.64-3.86 = 2.78 

pounds per square foot, 

or 2.78-7-144 = 0.0193 

of a pound per square inch. In this calculation the variation 
of the pressure of the atmosphere from 14.7 pounds per square 



136 STEAM-BOILERS. 

inch, and the effect of the reduction of pressure in the chimnev, 
have been neglected, as they are insignificant. 

To find the draught in inches of water we may consider that 
one cubic foot of water weighs 62.4 pounds. Consequently a 
column of water a foot square and which produces a pressure of 
2.78 pounds per square foot will be 



of a foot high, or 



2.78 H- 62.4 = 0.0606 
0.0606X12=0.727 



of an inch high. This is the draught that would be shown by 
a U-tube if the chimney were closed at the bottom. 

Areas of Chimneys and Flues.— In common practice it is 
found that satisfactory results are obtained if the area of the 
section of a chimney is made 1/10 the area of all of the grates 
connected to the chimney. 

The area of a chimney used for a small plant where there is 
only one or two boilers should be made 1/8 the area of the grate. 

The flue and uptake of a boiler is generally made 1/7 to 1/8. 
the grate area. 

Forms of Chimneys. — Chimneys are made of brick or of 
steel plates. Steel chimneys are always round; large brick 
chimneys are usually round; small ones may be round or square. 
A round chimney gives a larger draught-area for the same weight 
of material, and it presents less resistance to the wind. 

Plate V gives the general arrangement and some detail of 
two chimneys: one of brick, 175 feet high, and the other of 
steel, 200 feet high. The brick chimney is built in two parts: 
the outer shell, which resists the pressure of the wind; and the 
lining, which forms the flue proper, and which may expand 
when the chimney is full of hot gases without bringing any 
stress on the shell. The shell has a foundation of rough stone 
and one course of dressed stone at the surface of the ground. 
The brickwork is splayed out inside to cover the stone foun- 



SETTINGS, FURNACES, AND CHIMNEYS. 137 

dation, and is drawn in at the top to the same diameter as the 
inside of the lining. The external form of the top is mainly 
a matter of appearance. The finish of large tiles at the top 
sheds rain and keeps water from penetrating the brickwork. 
The outside of the shell has a straight taper from the base 
nearly up to the head. A system of internal buttresses, as 
shown in section at Fig. 3 and Fig. 4, gives the requisite stiff- 
ness to the shell without an excessive amount of material. 
The lining carries its own weight only, being protected from 
the wind by the external shell; it has a uniform diameter of 
6 feet inside, and varies in thickness from 12 inches at the 
bottom to 4 inches at the top. A rectangular flue with an 
arched top, leads into the chimney at one side of the founda- 
tion. 

The shell of the steel chimney is made of vertical half-inch 
plates at the base, and is splayed out to give additional bearing 
on the foundation. Above this portion the shell has a straight 
taper to the top ; the plates, each 4 feet wide, vary in thick- 
ness from 3/8 of an inch to 1/4 of an inch. At the top an 
external finish of light plate is given for the sake of appear- 
ance. The foundation is of red brick, with a course of stone 
at the surface of the ground, clamped by a wrought-iron strap. 
The shell is bolted through a foundation-ring made of cast-iron 
segments 4 inches thick, and a steel plate 2\ inches thick, by 
long bolts which take hold of anchor-plates bedded in the 
foundation. The lining of fire-brick varies in thickness from 
18 inches at the bottom to 4J inches at the top. It lies against 
and is carried by the steel shell. The internal diameter of the 
chimney is intended to be 10 feet; at places the size is a little 
larger on account of the arrangement of the lining. The lining 
is used to check the escape of heat through the steel shell. 
It adds nothing to the strength of the chimnev ; on the con- 
trary, it must be carried by the shell There is a chance that 
moisture may be harbored between the lining ana the shell 
and give rise to corrosion. Large steel chimneys are compar- 



'3« 



STEAM-BOILERS. 



atively recent, so that experience does not show whether lined 
or unlined chimneys are the more durable. 

Stability of Chimneys. — On account of the concentration 
of weight on a small area, and the disastrous results that would 
follow from defective work, the founaanons of an important 
chimney should be carefully laid by an experienced engineer. 
A natural foundation is to be preferred, but piling and other 
artificial methods of preparing the earth for the foundation can 
be used when necessary. Good natural earth should carry 
from 2000 to 4000 pounds to the square foot. The base of 
the chimney should be spread out so that this pressure, or 
whatever the earth can safely bear, may not be exceeded. 

In calculating the stability of a chimney it is customary 
to assume the maximum pressure 01 the wind as 55 pounds 
per square foot on a flat surface. The pressure of the wind 
on a round chimney would theoretically be two thirds of that on 
a square chimney. It is commonly assumed, however, that the 
pressure on a round chimney is 0.57 of that on a square chimney 
of the same width; on a hexagonal 0.75 and on an octagonal 0.65- 
This method has long been in use, and it has been shown to 
give abundant stability. Experiments on wind-pressure are 
difficult and uncertain, and, curiously, the pressure determined 
by small gauges is commonly in excess of that shown by large 
gauges. Thus, certain experiments made during the construc- 
tion of the Forth Bridge, gave a maximum wind-pressure of 
35 pounds per square foot on a large gauge 20 feet long and 
15 feet wide, while a small gauge showed a pressure of 41 pounds 
at the same time. The highest recorded pressure during violent 
gales, at the Forth Bridge, was that just quoted, namely 35 
pounds to the square foot. Small wind-gauges have shown 
a pressure of 80 to 100 pounds to the square foot; but such 
results are discredited, both because it is known that small 
gauges give too large results, and because buildings were not 
destroyed as they would have been if exposed to such wind- 
pressures. 



SETTINGS, FURNACES, AND CHIMNEYS. 139 

To determine whether a chimney is stable, treat it as a 
cantilever uniformly loaded with 55 pounds to the square 
foot and find the bending-moments and resultant stresses* 
The stress will be a tension at the windward side and a com- 
pression at the leeward side. Calculate the direct stress due 
to the weight of the chimney, which will be a compression at 
either side of the chimney. For a brick chimney, subtract 
the tension due to wind-pressure at the windward side from 
the compression due to weight : if there is a positive remainder 
showing a resultant compression the chimney will be stable ; 
otherwise not, because masonry cannot withstand tension. 
Again, add the compression due to wind-pressure to the com- 
pression due to weight, to find the total compression at the 
leeward side : if the result is not greater than the safe load on 
masonry, the chimney is strong enough. The safe load may 
be taken as 10 tons per square foot. 

Fig. 54 gives a graphical method of arriving at the stability 
of a chimney. At the point A, the centre of gravity of the trape- 
zoidal area against which the wind presses, a line is drawn at 
some convenient scale to represent the total wind-pressure on the 
side. From B a line BW, drawn at the same scale, represents 
the total weight of the chimney. 

Combine at point B these two forces, and if the resultant cuts 
the base at a point D, so that CD is less than 1/3 EE for square 
chimneys and less than 1/4 EE for round chimneys, there will be 
no tension on the mortar at the windward side, and the maximum 
intensity of compression will be twice the mean intensity. 

In the upper diagram at the right of the cut of the chimney 
the line YY represents the direct compression due to the weight 
of the chimney; the line XX the stresses due to the action of 
the wind. Combining these the line ZZ is obtained. This 
shows at the windward side a compression equal to EZ. 

The second diagram illustrates the case where the action of 
the wind just removes the compression at the windward edge, 
making EZ at the leeward edge equal to twice EY. 



140 



STEAM-BOILERS. 



The third cut shows a possible distribution of the stresses on 
a section which had cracked on the windward side. 

The calculation for the strength of a self-supporting steel 
chimney involves certain details of the design of a riveted joint 
and certain nice discriminations as to the action of such a joint 





Fig. 54. 



when affected by a bending moment, which are out of place 
here. For example, it is clear that on the leeward side the com- 
pression on a lapped joint must be borne by the rivets and that 
the plate between the rivets is free from stress. A crude calcu- 
lation may be made as for a homogeneous cylinder, which is 
subjected to compression and bending, using for the apparent 



SETTINGS, FURNACES, AND CHINNEYS. 



141 



working stress the safe stress of the steel, multiplied by the effi- 
ciency of the riveted joint, as determined by methods given in 
Chapter VIII. 

A calculation like that just described must be made for the 




Fig. 55. 



section of the chimney at the base, for each section where there 
is a change of thickness or of construction, and for any other 
section where there is reason to suspect weakness or instab- 
ility. 

A steel base built up from boiler-plate is shown by Fig. 55. 
This differs from the one shown on Plate V. 



142 STEAM-BOILERS. 

The lining of a brick chimney is to be calculated for com- 
pression due to weight, at the base and at each section where 
there is a reduction of thickness. The lining of a steel chim- 
ney must be counted in when the stress due to weight is 
determined. 

A separate calculation must be made for the stability of 
the foundation of a steel chimney. For this purpose find the 
total wind-pressure on the chimney and its moment about an 
axis in the plane of the base of the foundation. Find also 
the total weight of the entire chimney with its lining, and of 
the foundation : this will be a vertical force acting through 
the middle of the foundation. Divide the moment of the 
wind-pressure by the weight of the chimney and foundation : 
the result will be the distance from the middle of the founda- 
tion to the resultant force due to the combined action of 
wind-pressure and weight. If this resultant force is inside 
the middle third of the width of the foundation, the chimney 
will be stable. 

This brief statement is intended to describe the method 
of calculating the stability of chimneys, and not to give full 
instructions. The design and calculation for an important 
chimney should be intrusted only to a competent engineer 
who has had experience in such work. 

The subject of chimneys is discussed quite fully and many 
drawings given in a work by Mr. W. W. Christie on "Chimney 
Design." 






CHAPTER VI. 
POWER OF BOILERS. 

THE power of a boiler to make steam depends on the 
amount of heat generated in the furnace, and on the propor- 
tion of that heat which is transferred to the water in the 
boiler. The amount of heat generated depends on the size 
of the grate, the rate of combustion, and the quality of the 
coal burned. The transfer of heat to the water in the boiler 
depends on the amount and arrangement of the heating-sur- 
face. In practice it is found that each type of boiler has 
certain general proportions which give good results ; any 
marked variation from these proportions is likely to give poor 
economy in the use of coal, or to lead to excessive expense in 
construction. 

The capacity of a boiler is commonly stated in boiler 
horse-power; the economy of a boiler is given in the pounds 
of steam made per pound of coal. Neither method is entirely 
satisfactory, but definite meaning is attached to the terms 
by definitions and conventions. 

Standard Fuel.— A comparison of the composition and 
of the total heats of the several kinds of coal given in the 
table on page 51 shows a great difference in the value of a 
pound of coal, depending on the district and mine from which 
it comes. In order to introduce some system into the com- 
parison of the performance of boilers in different localities it 
has been proposed that some coal or coals be selected as 
standards, and that all boiler-tests intended for comparison 
be made with a standard coal. For this purpose it has been 

143 



144 STEAM-BOILERS. 

proposed to select Lehigh Valley anthracite, Pocahontas 
semi-bituminous, and Pittsburg bituminous coal. More def- 
inite comparisons would result if only one coal, such as Poca- 
hontas, were selected. The objections are, first, that some 
trouble and expense might be incurred in localities where 
this coal is not regularly on the market ; and second, that 
a furnace designed for a given coal may not give its best 
results with a different kind of coal. There is a notable dif- 
ference between furnaces designed for anthracite coal and 
those designed for bituminous coal ; for the rest it appears 
that the use of a standard coal is a question merely of ex- 
pediency. 

In making a boiler-test it is not difficult to make an ap- 
proximate determination of the per cent of ash in the coal 
used. When that is done, the economy is usually stated in 
terms of water evaporated per pound of combustible, as well 
as per pound of coal. This gives somewhat more definite- 
ness to the statement ; but as no account is taken of the vola- 
tile matter in the coal, nor of the oxygen, this method also is 
indefinite. 

Value of Coal. — The actual value of a coal for making 
steam can be determined only by accurate tests with a fur- 
nace and boiler which are adapted to develop and use the 
heat that the coal can produce. While many boiler-tests 
have been made, and there is a good deal of material that 
could be used for the purpose, there has not yet been made a 
satisfactory statement of the value of the fuel in common use. 

It appears probable that the real value of a coal for mak- 
ing steam is proportional to the total heat of combustion. If 
this can be shown to be true, then coals should be sold on the 
basis of heat of combustion, just as steel is required to have 
certain physical properties which are determined by making 
proper tests. 

Quality of Steam. — When the economy of a boiler is 
stated in terms of water evaporated per pound of coal, it is 
assumed that all the water is evaporated into dry saturated 



POWER OF BOILERS. 1 45 

steam. But the steam which leaves the boiler may contain 
some water, or it may be superheated. 

The moisture carried along by steam is called priming. 
The steam from a properly designed boiler, working within its 
capacity, seldom carries more than three per cent of priming. 
Under favorable circumstances steam from a boiler will be 
nearly dry. 

If steam, after it passes away from the water in the boiler, 
passes over hot surfaces it will be superheated ; that is, raised 
to a temperature higher than that of saturated steam at the 
same pressure. Vertical boilers with tubes through the steam- 
space give superheated steam. If steam is to be superheated 
to any considerable extent, it must be passed through a 
superheater, either attached or independently-fired, as described 
in Chapter II. Boilers of the Manning type and boilers equipped 
with attached superheaters generally give more superheat when 
forced. This is because of the higher temperature of the escaping 
gases. 

Although the consumption of an engine, figured on pounds of 
steam, is less with superheated steam than with saturated steam, 
it does not necessarily follow that the coal per indicated horse- 
power per hour is less. A number of plants investigated by the 
writers have shown an increased coal consumption. 

Certain types of turbine must be supplied with superheated 
steam, if any economy is to be obtained, on account of the fact 
that any water in the shape of priming in the steam or any water 
resulting from the expansion of the steam acts like a water-brake. 
In some turbines it is estimated that one per cent priming causes 
two per cent loss in economy. 

Steam-space. — The steam-space and the free surface for 
the disengagement of steam should be sufficient to provide for 
the efficient separation of the steam from the water. Cylin- 
drical tubular boilers frequently have the steam-space equal to 
one third of the volume of the boiler-shell. Marine return- 
tube boilers usually have a smaller ratio of steam-space to 
water-space. 



I4& STEAM-BOILERS. 

The more logical way appears to be to proportion the 
steam-space to the rate of steam-consumption by the engine. 
Thus the ratio of the volume of the steam-space of cylindri- 
cal boilers to that of the high-pressure cylinder of multiple- 
expansion engines varies from 50 : 1 to 140 : 1. The ratio of 
the steam-space of a simple locomotive-engine to the volume 
of the two cylinders is about 6J : 1. 

The capacity of the steam-space is sometimes equal to the 
volume of steam consumed by the engine in 20 seconds. It 
was found in some experiments with marine boilers having a 
working-pressure less than 50 pounds per square inch, that a 
considerable quantity of water was carried away by the steam 
when the steam-space was equal to the volume of steam con- 
sumed in 12 seconds, but that no water was carried into the 
cylinders when the steam-space was equal to the volume of 
steam used in 1 5 seconds and that no trouble from water was 
ever experienced when the steam-space was proportioned for 
20 seconds. 

All the preceding discussion refers to engines that run at a 
considerable speed of rotation — not less than 60 revolutions 
per minute. Engines that make but few revolutions per min- 
ute and take steam for only a portion of the stroke require a 
larger proportion of steam-space. As an example we may 
cite the walking-beam engines for paddle-steamers. 

Equivalent Evaporation.— The heat required to evapo- 
rate a pound of water depends on the temperature of the feed- 
water, the pressure of the steam, and the per cent of priming. 

For example, if water is supplied to a boiler at 140 F., 
and is evaporated under the pressure of 80.3 pounds by the 
gauge, with 2 per cent of priming, the heat required will be 
calculated as follows: 

The heat of the liquid at 140 F., or the heat required to 
raise a pound of water from 32 F. to that temperature, is 
108.2 B. T. U. The heat of the liquid at 95 pounds abso- 
lute, corresponding to 80.3 pounds by the gauge, is 294.3 



POWER OF BOILERS. 147 

B. T. U. Consequently the heat required to raise the feed- water 
up to the temperature of the boiler is 

294.3 — 108.0 = 186.3 B. T. U. 

The heat of vaporization, or the heat required to change a 
pound of water into steam, at 95.0 pounds absolute, is 886.4 
B. T. U. But 2 per cent of water is found in the steam which 
comes from the boiler, leaving 98 per cent of steam ; consequently 
the heat required is 

0.98X886.4 = 868.7 B. T. U. 

The total amount of heat is therefore 

186.3 +868.7 = 1055.0 B. T. U. 

Suppose that each pound of coal evaporates 9 pounds of 
water, then the heat per pound of coal transferred to the boiler 
is 

9 X 1055.0 =9495-° B. T.U. 

Now the heat required to vaporize a pound of water at 212 
F., under the pressure of the atmosphere, is 966.3 B. T. U. 
Dividing the thermal units per pound of coal by this quantity 
gives 

9495.0^966.3=9.83, . 

which is called the equivalent evaporation from and at 212 F. 

This method of stating the economy of a boiler is equivalent 
to using a special thermal unit 966.3 as large as the thermal unit 
defined on page 54. 

In making calculations involving quantities of wet steam 
it is convenient to consider the amount of steam present, 
rather than the percent of priming. In the example just con- 
sidered, there are 0.02 of water or priming, and 0.98 of steam. 
The part of a pound which is steam is represented by x. 

If the heat of vaporization at the pressure of the steam in 
the boiler is represented by r, the heat of the liquid at that 
pressure by q } and the heat of the liquid at the temperature 
of the feed-water by q ; and if, further, there are w pounds of 



148 STEAM -BOILERS. 

water evaporated per pound of coal, — then the equivalent 
evaporation is 

w{xr + q — g ) 
966.3 

The highest equivalent evaporation per pound of coal is 
about 12 pounds, and to accomplish this result about 80 per cent 
of the total heat of combustion must be transferred to the water 
in the boiler. The complete combustion of a pound of carbon 
develops 14,650 B. T. U. ; if all this heat could be applied to 
vaporizing water at 212 F., then the amount of water evap- 
orated would be 

14,650 -r- 966.3 = 15-j- pounds. 

Few, if any, coals have a greater heat of combustion, con- 
sequently this figure may be considered to be the maximum 
equivalent evaporative power of coal. 

Should any test appear to give a larger evaporative power, 
or even a power approaching this result, it may be concluded 
either that there is an error in the test, or that there is a large 
amount of priming in the steam. Some tests of early forms 
of water-tube boilers without proper provisions for separating 
water from the steam, appeared to give extraordinary results; 
which results were due to the presence of a large amount of 
priming in the steam. At that time the methods used for 
determining the amount of priming were difficult and uncer- 
tain, and were frequently omitted in making boiler-tests. 

Boiler Horse-power — It has always been the habit to 
rate and sell boilers by the horse- power. The custo'm appears 
to be due to Watt, and at that time the horse-power of a 
boiler agreed very well with the power of the engine with 
which it was associated. The traditional method of rating 
boilers, coming down from that time, was to consider a cubic 
foot, or 62J- pounds per hour, of water evaporated into steam, 






POWER OF BOILERS. 149. 

as equivalent to one boiler horse-power. This rating is now 
antiquated, and is seldom or never used. 

It is now customary to consider 30 pounds of water evap- 
orated per hour from a temperature of ioo° F., under the 
pressure of 70 pounds by the gauge, as equivalent to one 
horse-power. This standard was recommended by a com- 
mittee of the American Society of Mechanical Engineers.* 

This standard is equivalent to the vaporization of 34.5 
pounds of water per hour from and at 2 12 F. ; it is frequently 
so quoted. It is also equivalent to 33,320 B. T. U. per hour. 

Since the power from steam is developed in the engine, 
and. since the economy in the use of steam depends on the 
engine only, and may vary widely with the type of engine, it 
appears illogical to assign horse-power to a boiler. The 
method appears to be justified by custom and convenience. 

Rate of Combustion. — The rate of combustion is stated 
m pounds of coal burned per square foot of grate- surface per 
hour. It varies with the draught, the kind of coal, and. the 
skill of the fireman. 

In general a slow or moderate rate of combustion gives 
the best results, both because the combustion is more likely 
to be complete and because the heating-surface of the boiler 
can then take up a larger portion of the heat generated. A 
very slow rate of combustion may be uneconomical, because 
there is a large excess of air admitted through the grate, and 
because there is a larger proportionate loss of heat by radia- 
tion and conduction. It is claimed that forced draught may 
be made to give Complete combustion with a small amount of 
air in excess, and that it should give better economy than 
slower combustion. It will be remembered that a small 
amount of carbon monoxide due to incomplete combustion 
will cause more loss than a large amount of air in excess. 

Heating-surface. — All the area of the shell, flues, or 

- Trans., voi. vi, 1881. 



150 STEAM-BOILERS. 

tubes of a boiler which is covered by water, and exposed 
to hot gases, is considered to be heating-surface. Any 
surface above the water-line and exposed to hot gases is 
counted as superheating-surface. The upper ends of tubes 
of vertical boilers are in this condition. 

For a cylindrical tubular boiler the heating-surface in- 
cludes all that part of the cylindrical shell which is below the 
supports at the side walls, the rear tube-plate up to the brick- 
arch which guides the gases into the tubes, and all the inside 
surface of the tubes. The front tube-plate is not counted as 
heating-surface. 

For a vertical boiler like the Manning boiler (page ai) 
the heating-surface includes the sides and crown of the fire- 
box and all the inside surface of- the tubes up to the water- 
line. Surface in the tubes above the water-line is superheat- 
ing-surface. A certain 200-H.P. boiler of this type has 1380 
square feet of heating-surface and 470 square feet of super- 
heating-surface. 

The heating-surface of a locomotive-boiler consists of the 
sides and crown of the fire-box and the inside surface of the 
tubes. 

The heating-surface of a Scotch boiler consists of the 
surface of the furnace-flues above the grate and beyond the 
bridge, the inside of the combustion-chamber, and the inside 
surface of the tubes. 

The effective surface of any tube-plate is the surface re- 
maining after the areas of the openings through the tubes is 
deducted. 

Relative Value of Heating-surface. — A review of the 
kinds and conditions of heating-surface in various kinds of 
boilers, or even in a particular boiler, shows that the value of 
heating-surface varies widely. It does not appear possible to 
assign values to different kinds of heating-surface. We will 
note only that surfaces like the shell of a cylindrical boiler 
over the fire, like the inside of a fire-box, or like the flues of 



POWER OF BOILERS. 



i=;i 



a marine boiler, which are exposed to direct radiation from 
the fire, are the most energetic in their action. Surfaces 
like combustion-chambers and tube -plates, against which the 
flames play, are nearly if not quite as good. The inside of 
small flues and tubes is less favorably situated, more especially 
^sthe flame is, under ordinary conditions, rapidly extinguished 
after it enters such a flue or tube. The length of the flame 
m small tubes depends on the draught, and with very strong 
forced draught may extend completely through tubes of some 
length. 

The value of heating-surface in a tube rapidly decreases 
with the length. It is doubtful if there is any advantage in 
makmg the length of a horizontal tube more than fifty times 
the diameter. Tubes of vertical boilers should have twice 
that length. 

Ordinary Proportions. — The following table gives the 
ordinary proportions of various types of boilers: 



Type of Boiler. 



Lancashire 

Cylindrical multitubular. 
Vertical, Manning 

Locomotive 

Locomotive type, sta- 
tionary .- 

Scotch marine 

Water-tube with cylin- 
der or drum 

Water - tube with sepa- 
rator. 



" 3 
rtJ3 



8 to 12 

8 to 15 

10 to 20 

50 to 120 

average 75 



8 to 
35 to 



15 

45 



9 to I S 

15 to 67 
average 20 



O u O 
C/5 



25 to 30 
35 to 40 
*43+ 16 
60 to 70 



40 to 45 
30 

35 to 45 

30 to 40 



> 6 



cr> 
«W 

bs| 

> « u 
< 



8 to 10 

9 to 10.5 
9 to 10.5 

6.7 to 8.5 

9 to 10.5 
7 to 9 

9 to 10.5 

7 to 9 



(A 


O.36 


O.3O 


0.23 


0.07 


0.30 


O.II 


0.28 


0.22 






in 



c 



7.0 

". 5 

11. 1 

4-5 



12.6 
3-3 

11. o 

7.3 



*48 heating-surface, 16 superheating-surface. 



The higher rates of evaporative economy are associated 
with slower rates of combustion and with larger ratios of 
heating-surface to grate-surface. 



STEAM-BOILERS. 



No attempt is made to distinguish the kind or location of 
heating-surface ; it must be understood that the ordinary ar- 
rangements and proportions for the several types are followed 
if this table is to be used in designing boilers. For example, 
it cannot be expected that heating-surface gained by length- 
ening the tubes of a locomotive-boiler will add materially to 
the efficiency of the boiler. 

This table has been compiled from a large number of ex- 
amples, and may be taken to represent current good practice. 
The last two columns giving the grate-surface and heating- 
surface have been computed on the basis of one horse-power 
for 34.5 pounds of water evaporated per hour from and at 
212° F. 



CHAPTER VII. 
STAYING AND OTHER DETAILS. 

ALL plates of a boiler that are not cylindrical or hemispher 
ical require staying to keep them in shape. For example, 
the cylindrical shell of a cylindrical tubular boiler does not 
require staying, because the internal pressure tends to keep it 
cylindrical. On the other hand, the pressure tends to bulge 
out the flat ends, and they must be held in place against that 
pressure. 

Many different methods of staying will be found in the 
different types of boilers seen in practice, and there are fre- 
quently several ways of staying the same kind of a surface. 
A few methods will be described in a general way. The 
placing of stays and arrangement of details is an important 
part of the design of a boiler, and must be worked out for each 
special design. 

Cylindrical Tubular Boiler. — The parts of the tube-sheets 
at the ends of a cylindrical tubular boiler, through which the 
tubes pass, are sufficiently stayed by the tubes themselves. 
The flat ends above the tubes require staying. Also, if there 
is a manhole at the bottom of the front end, the space thus 
left unsupported requires staying, and there is a corresponding 
space at the back end. 

An elaborate set of tests was made by Messrs. Yarrow'" and 
Co., to determine the holding-power of tubes expanded into 
a tube-sheet. It was found that from 15,000 to 22,000 pounds 



* London Engineering, Jan. 6, 1893. 

153 



154 STEAM-BOILERS. 

were required to pull out a two-inch steel tube ; in some cases 
the tube gave way by tension inside the head into which it 
was expanded. 

The staying of a flat surface consists essentially in hold- 
ing it against pressure at a series of isolated points, which are 
arranged in a regular or symmetrical pattern. A simple case 
of staying is found in the side sheets of a locomotive fire-box. 
Here the stays, which are arranged in horizontal and vertical 
rows, are screwed and riveted. If possible, the pitch or dis- 
tance between the supported points should be the same, but 
this is possible only when arranged in rows as just men- 
tioned. The allowable pitch depends on the thickness of 
the plate. For cylindrical tubular boilers the pitch of the 
supported points of the flat ends above the tubes is 3.5 to 5 
inches. The outside fibre-stress in the plate stayed may be 
from 6000 to 9000 pounds per square inch ; the calculation of 
this stress involves a knowledge of the theory of elasticity, and 
will be referred to later. 

It is not advisable, for this type of boiler, to assign a sepa- 
rate stay to each supported point of the flat surface under 
discussion, consequently the points are grouped, each point of 
the group being riveted to some support inside the boiler, 
and then the supports are held by proper stays. 

A good method of staying the flat end of a cylindrical 
boiler is shown by Plate I, and also, with some further details, 
by Fig. 56. There are two 6-inch channel-bars of proper 
length, that are riveted to the flat head. The rivets tie the 
plate to the channel-bars and thus support the plate at iso- 
lated points. The channel-bars in their turn are supported by 
stays that run directly through the boiler and have nuts and 
washers at each end. The channel-bars act as beams, and must 
be capable of carrying the load due to the pull on the rivets, 
and the through-stays must carry the loads on the beams. 
A short piece of angle-iron is riveted to the upper side of the 
upper channel-bar; it carries five additional rivets in the flat 



STAYING AND OTHER DETAILS. 



155 



head, and adds an additional load to the upper channel-bar. 
The points where the through-stays pass through the head 
are supported directly by the stays through the washers and 
nuts. 

The lower channel-bar is a continuous girder with four spans 
and five supports. The stays form three supports and the 
other two are at the inner edge of the flange of the head. 
The upper channel-bar is a girder with three spans and four 




FRONT HEAD FOR 
84-3"TUBES 

Fig. 56. 



supports. The calculation of the stresses in the channel- 
bars is somewhat unsatisfactory, largely because the support 
at the flange of the head is uncertain; and this support must 
be left with some flexibility, and consequently with soem 
uncertainty, as too great rigidity leads to grooving. 

In arranging such a staying, we begin by determining the 
allowable pitch of the points supported by the rivets, assuming 
them to be in equidistant horizontal and vertical rows. This 
allowable pitch must not be exceeded, but the pitch may be 
made less either horizontally or vertically, or in both ways. 

A space of at least three inches is left between the top 



156 STEAM-BOILERS. 

row of tubes and the lowest row of rivets, and a similar space 
is left at the sides. This is to avoid grooving 

The two upper through-stays are fifteen ana a half inches 
apart on centres. They must be wide enough apart to allow 
a man to pass through. 

The stay-rods are upset at the ends so that the diameter 
at the bottom of the threads is greater than the diameter of 
the body of rod. The washer outside the plate may be 
made of copper, in which case it is made cup-shaped so as to 
bear on a narrow ring, and is made tight by calking; or the 
washer is made of iron, and is bedded in red lead to make 
a joint. Sometimes cap-nuts are used outside the head to 
prevent the escape of steam that may leak around the screw- 
threads. Long stay-rods are sometimes supported at the 
middle. 

A method of staying otherwise similar to that just de- 
scribed, uses two angle-irons in place of a channel-bar. A 
washer of special form is used to give a proper bearing, for 
the inner nut on the through-stay, against the angle-irons. 

Fig. 57 shows a different method of staying for cylin- 
drical boilers. The left half of the figure represents the end 
elevation, and the right half represents a section through the 
manhole; this is a common method for boiler drawings. 
The supported points are arranged in sets of four, and are 
tied to forgings known as crowfeet. Fig. 58 represents such 
a crowfoot with four rivets, known as a double crowfoot; 
a single crowfoot with only two rivets is shown by Fig. 59. 
When crowfeet are used they may be- arranged in various 
patterns , in the example given there is a horizontal row of 
five double crowfeet just above the tubes, and three other 
double crowfeet are arranged in a circular arc. At the ends 
of the arc there are two braces like Fig. 60, which are used 
instead of single crowfeet. From each crowfoot a diagonal 
stay is carried to the boiler-shell. These stays are flattened at 
rhe farther end and bent to lie against the side of the shell, to 



STAYIXG AXD OTHER DETAILS. 



157 



which they are riveted with two or three rivets ; the arrange- 
tnent is similar to that of the right-hand end of the brace 




0^ 




i°\ 


— 






°) 


^ ° 


h*1 



Fig. 58. Fia 59> 

shown by Fig. 60. At the crowfoot the stay has a forked 
head through which a bolt passes under the arch of the 



Itf 



STEAM-BOILERS. 



double crowfoot. A nut holds the bolt in place and pre 
vents the head of the stay from spreading. 







Fig. 62 



A combination of channel-bar and crowfeet is shown by 
Fig. 61. The double crowfeet are represented as made of 
boiler-plate, bent up as shown by Fig. 62. 



STAYING AND OTHER DETAILS. 



J 59 



A method of staying, suitable only for boilers which 
work under low steam-pressure, is shown by Fig. 63. Short 
pieces of T iron, arranged radially, are riveted to the head. 
Each T iron is supported from the cylindrical shell by two 




OOOOOO OOOOOO 
OOOOOO OOOOOO 



Fig. 63. 

diagonal stays; one of the stays Is represented by Fig. 64. 
One end of the stay is split, and is pinned to the T iron; 
the other end is flattened, and riveted to the shell. 

The shell of a cylindrical boiler, whether it is a tubular or 
a flue boiler, is made of a series of sections or rings. Each 




Fig. 64. 

ring is made of one or two plates riveted along the edge, or 
longitudinal seam. This seam has at least two rows of rivets; 
more complicated joints are commonly used to give more 
strength to the seam. Alternate rings of the shell are made 
smaller so that they may be slipped inside the rings at each 
of their ends. The seams joining adjacent rings are com- 
monly single-riveted. The longitudinal seams are kept above 



i6o steam-boilers. 

the middle of the boiler, so that they are not exposed to the fire. 
The first ring at the front end is always an outside ring, so that 
the first ring-seam has the outside edge pointing away from the 
fire; there is consequently less liability of injury to the seam 
from the flames that pass under the boiler toward the back end. 

Fig. 65 shows what is known as the Huston brace. It takes 
the place of the braces shown by Figs. 60, 62, and 64. It is made 
without welds. 

All horizontal multitubular boilers, 60 inches or over in diam- 
eter, should have a manhole in the front head, as shown by Fig. 174 
in Chapter XII. The manhole frame is itself sufficiently stiff to 
reinforce the bottom of the front head, but the back head must 



Fig. 65. 

be stayed. Ten or twelve tubes must be omitted in order to 
make room for the manhole. Fig. 66 shows a good method of 
staving the back head between the tubes and the shell. 

Two pieces of angle iron are riveted to the plate with a dis- 
tance piece or ferrule made of a piece of pipe or tube between the 
plate arid the bottom of the angle irons. These ferrules hold the 
angle iron off from the plate 2 to 3 inches. 

This distance allows of a free circulation of water and pre- 
vents an overheating of the plate. A space 2 inches deep will 
be sufficiently great to prevent scale from bridging over the space 
between the angle iron and the plate. Rivets are pitched from 
5 to 8 inches along the angle irons. 

Bolts commonly made with tapering heads fitting conical 
holes in the plate pass between the angle irons and are drawn 
tight by nuts. 

Two stay-rods flattened at one end are fastened to the angle 
irons, as shown. These rods lead at a slight angle through the 



STAYING AND OTHER DETAILS. 



161 




1 62 STEAM-BOILERS. 

front head, one at either side of the manhole frame, and are 
fastened by nuts. The threaded ends are upset to a diameter 
greater than the centre of the rod. The angle at which the rods 
run across the boiler is so slight that there is no trouble with the 
nuts at the front head. These rods should never be tied to the 
bottom shell. Huston braces should not be used or any system 
which ties to the shell. 

Vertical Boilers.— The tube-sheets of a vertical boiler, 
as is evident from inspection of Figs. 6 and 7, are usually stayed 
sufficiently by the tubes. Should the upper tube-sheet be much 
larger than the crown of the fire-box, it may need staying be- 
tween the tubes and the shell. Stays like Fig. 60 may be used 
for this purpose. 

The circular fire-box of a vertical boiler is subjected to 
external pressure, and is prevented from collapsing under that 
pressure by tying it to the outer shell by screwed stay-bolts, 
which are put in and set like the stay-bolts for a locomotive- 
boiler. 

Locomotive-boiler. — The parts of a locomotive-boiler 
that require staying are the fire-box and the flat ends. The 
tube-sheets are sufficiently stayed by the tubes, but there is a 
part of the tube-sheet at the smoke-box end and a part of the 
flat end above the fire-box which requires support. The prob- 
lems here resemble those met in staying the tube-sheets of a 
horizontal cylindrical boiler, and similar methods are used. 
Thus in Plate II there are shown eight through-stays, each ij 
of an inch in diameter. These stays pass through the girder 
staying of the crown-sheet, and have a simple nut and washer 
outside the end-plates of the boiler. At the smoke-box end, 
as shown by Figs. 1 and 3, Plate II, there are two diagonal 
stays taking hold of single crowfeet and running to the middle 
of the barrel. At the fire-box end there are four crowfeet or 
short angle-irons, made by bending up boilerplate; two are 
shown by the right-hand elevation of Fig. 2 on Plate II. The 
outer crowfeet have five rivets, and the others six. From the 
outer crowfeet diagonal stays run to the shell at the ring just 



STAYING AND OTHER DETAILS. 163 

in front of the fire-box. From the inner crowfeet stays run to 
the middle ring of the boiler. There are also two stays like 
Fig. 60, which run to the shell above the fire-box. Finally, 
there is a crowfoot and stay at the middle of the row of eight 
through-stays, this stay fastening to the two end crown-bars. 

Below the tubes there is a place in the fire-box tube-sheet 
which requires support. This is given by three braces like 
Fig. 60, as shown by Figs. 1 and 2, Plate II. The shell of 
the boiler, shown by this plate, is higher over the fire-box than 
it is at the barrel, and a ring of peculiar shape is required to 
join the two parts together. This ring is cylindrical below and 
conical on top ; at the sides there are flattened spaces which 
require stiffening to prevent them from springing, and thus 
start grooving of the plates. For this purpose there are three 
T irons riveted to the shell at the flattened place mentioned, 
as shown by Fig. I, Plate II. The upper ends of the T irons 
on opposite sides of the boiler are tied together by transverse 
stays above the tubes. 

Coming now to the fire-box of the boiler represented by 
Plate II, we find that at the front, rear, and sides it is tied to 
the external shell by screwed stay-bolts set in equidistant hor- 
izontal and vertical rows. The holes for these stay-bolts are 
punched or, better, drilled before the fire-box is in place. After 
it is in place and riveted to the foundation-ring a long tap is 
run through both plates, the fire-box plate and the shell, and 
thus a continuous thread is cut in the plates. A steel bolt is 
now screwed through the plates, cut to the proper length, and 
riveted cold at each end. Owing to the screw-thread on the 
bolts, this riveting is imperfect, and likely to develop cracks at 
the edge. The thread should be removed from the middle 
of the bolts, as they are then less liable to crack under the 
peculiar strains set up by the unequal expansion of the fire- 
box and outside shell. 

The stay-bolts are very likely to be cracked or broken on 
account of the expansion of the fire-box; to detect such a 



1 64 STEAM-BOILERS. 

failure of a bolt, or to show when excessive corrosion has taken 
place, the stay-bolts are often drilled from the outer end nearly 
through to the inner end. In case of failure steam will blow 
out of the defective stay ; serious injury has often been avoided 
by this method. 

The crown-sheet of the fire-box is exposed to intense heat, 
and is covered with only a few inches of water. The problem 
of properly staying this flat crown-sheet without interfering 
with the supply of water to it is one of the most difficult 
problems in locomotive-boiler construction. Figs. I and 2, 
Plate II, show the method of staying a crown-sheet with a sys- 
tem of girder-stays. Above the crown-sheet there are fourteen 
double girders, which are supported at the ends by castings of 
special form, shown by Figs. 2 and 6; the castings rest on the 
edges of the side sheets and on the flange of the crown-sheet* 
In addition the girder-stays are slung to the shell by sling- 
stays. At intervals of four and a half inches the crown-sheet 
is supported from the girders by bolts, having each a head in- 
side the fire-box, as shown by Fig. 5, and a nut at the top 
bearing on a plate above the girder. These plates are turned 
down at the ends to keep the two halves of the girder from 
spreading. There is a copper washer under the head of each 
bolt, inside the fire-box, to make a joint. Between the girder 
and the crown-sheet each bolt has a conical washer or thimble 
to maintain the proper distance between the girder and crown- 
sheet. This thimble is wide above to bear on the girder, and 
small below to avoid interfering with the flow of water to the 
crown-sheet, and also so as to cover as little surface as possible 
on account of the danger of burning the crown-sheet wherever 
the metal is thickened. The whole system of girders is tied 
together, and the girder nearest the fire-door is tied to the 
outside shell, thereby serving as stage for the head. It is evi- 
dent that such a system of staying is heavy, cumbersome, and 
complicated. It is also uncertain in its action, since the equal- 
ization of stresses depends on a nice adjustment of the mem- 



STAYING AND OTHER DETAILS. 



I6 5 



bers of the system, which adjustment is liable to derangement 
from expansion of the fire-box. The girders or crown-bars are 
sometimes run lengthwise instead of transversely, but as the 
fire-box is longer than wide such an arrangement is inferior. 

To avoid the cumbersome method of staying the crown- 
sheet, which has just been described, the fire-box end of the 
boiler has been made flat on top, as shown by Fig. 67. The 




+ -r + -t+ . 
+ + -H-+1-'! 

f+-H- + t 
-H- + + + 1-JI 
+*+ -I- + t +;' 
-t- + -+— t + •+■! 
+-+-H--H-J! 
4 -f 1 + + i 1; 

'+-I- + + + + 

+ W-+-»- + -Hi 
■+-*■+ +4-+S 




Fig. 67. 

crown-sheet can now be stayed to the outside shell by through- 
stays having nuts and copper washers at each end. The flat 
side sheets of the shell above the fire-box are also stayed by 
through-stays, and there are also three longitudinal through- 
stays in the corners of the shell over the fire-box where it 
protrudes beyond the barrel. This forms what is known as 
the Belpaire fire-box, from the inventor. 

Fig. 68 shows an attempt to combine the use of through- 
stays, like those of the Belpair fire-box, with a cylindrical top 
above the crown-sheet. It will be noted that the stays are 
neither perpendicular to the crown-sheet nor radial when they 
pierce the shell, and they must be subjected to an awkward 
side pull at both places. 

The locomotive-boiler represented by Plate III has a 
Belpair fire-box, and shows in addition some peculiarities of 



1 66 



STEAM-BOILERS. 



staying. Thus the flat end-plate above the fire-box has 
four T irons riveted to it. Each T iron is tied to the shell 
by two diagonal stays. Each stay has the usual double 
head at the T iron ; the other end lies between, and is pinned 
to the flanges of pieces of plate that are riveted to the shell 
of the boiler. This arrangement is shown by the transverse 




and longitudinal sections through the fire-box. It will be 
noticed that the lower diagonal stays from the end-plate 
interfere with four transverse through-stays. These stays are 



STAYIXG AXD OTHER DETAILS. 



167 





W-s 



cut off and carry short vertical yokes, which are connected 
by two smaller rods, one above and one below the diagonal 
stays. 

The rings forming the barrel of the locomotive are made 
progressively smaller from the fire-box to the smoke-box; the 
slight taper toward the front end of the locomotive is found 
convenient in the design of the machine. 

Fig. 69 shows two ways of making the furnace-mouth of 
a locomotive-boiler. In one way the end- 
plate of the boiler-shell and the corre- 
sponding plate of the fire-box are flanged 
Yr\ in the same direction, and are riveted out- 
side of the boiler. In the other case the 
two plates are flanged into the water-space 
and the overlapping edges are riveted. 

Marine Boiler. — The parts requiring 
staying in the Scotch boiler are the flat 
ends, the furnaces, and the combustion- 
chambers. The flat ends above the tubes 
Fig. 69. are stayed by through-stays with nuts inside 

and with washers and nuts outside the plate. The boiler 
shown by Fig. 11, page 17, has two rows of through-stays 
— four in the upper and six in the lower row; two of the 
upper row pass through the fitting which carries the steam- 
nozzle. 

It is found in practice that the tube-sheets of a marine 
boiler are not sufficiently stayed by plain tubes expanded 
into the sheets. It is customary to make a portion of the 
tubes thicker than the others, and to provide these thick 
tubes with thin nuts outside the tube-plates, so that they may 
act more effectively as stays. The thick tubes in Fig. 11 are 
indicated by heavy circles. Sometimes every other tube of 
each second row is made a thick tube; that is, something - 
more than one fourth of the tubes are stay-tubes. Usually 
the number is fewer than this. 



1 68 STEAM-BOILERS. 

Below the tubes the front plate is supported in part by the 
furnace-flues, and in part by through-stays running to the 
combustion-chamber. There are two such stays above the 
furnaces and three below the furnaces in the middle of Fig. 
II, each if of an inch in diameter. There are also two stays 
2% inches in diameter, one at each side and above the fur- 
naces. These last stays have one point of attachment to the 
front end-plate, but each has two points of attachment to the 
combustion-chamber. For this purpose the rear ends of the 
stays are bolted to V-shaped forgings, similar to that shown 
by Fig. 70, page 169. 

The furnace-flues are corrugated to stiffen them, and thus 
maintain their form under the external pressure to which they 
are subjected. The corrugations in Fig. 11 are made up of 
alternate convex and concave semicircles; other forms of 
corrugations and other methods of stiffening flues, together 
with a discussion of the strength of flues, will be given in the 
next chapter. The front ends of the furnace-flues in Fig. 11 
are made as large as the outside of the corrugations; the rear 
ends are as small as the inside of the corrugations. Such an 
arrangement makes it easy to remove the furnaces without 
disturbing the other parts of the boiler and without destroy- 
ing the flues. 

The combustion-chambers of a Scotch boiler are made up 
of flat or curved plates subjected to external pressure, and 
must be stayed at frequent intervals to prevent collapsing. 
The sides and bottom of the combustion-chamber in Fig. 11 
are stayed to the cylindrical shell of the boiler by screwed 
stay-bolts, spaced seven inches on centres. The back of the 
combustion-chamber is stayed in like manner to the back end 
of the boiler, and thus both of these flat surfaces are secured. 
The plates used for making the combustion-chamber are 
thicker than those used for a locomotive fire-box, and conse- 
quently the stays are spaced wider and are larger in diameter. 

The top of the combustion-chamber is stayed by stay- 



STAYING AND OTHER DETAILS. 



169 



bolts and bridges in a manner that suggests the crown-bar 
staying of a locomotive fire-box. The space is, however, 
narrower and the staying is less complicated. 

Complex Stays. — Sometimes the points to be connected 
by stays are so numerous that too many through-stays will be 




Fig. 70. 

required if all points are stayed separately. Thus in Fig. 70 
there is a tee-iron riveted to a flat plate, and supported 
at intervals, as indicated by the two bolts passing through 
it. Instead of using a through-stay for each bolt, the bolts 
are coupled by two V-shaped forgings, which forgings are 
bolted to a through-stay at the angle of the V. There 
is enough freedom of the bolts in their holes to give equal 
distribution of the pull on the through-stay. By an exten- 
sion of this method several points may be supported by one 
stay-rod. 

Gusset-stays. — The flat ends of the Lancashire boiler, 
shown by Fig. 4, page 7, are secured to the cylindrical shell 
by gusset-stays; such a stay is shown more in detail by Fig. 
71. A plate is sheared to the proper form, and is riveted 



I/O 



STEAM-BOILERS. 



between two angle-irons along the edges that come against 
the shell and the flat end. The angle-irons in turn are riveted 
to the shell or to the flat plate. Gusset-stays have the 
advantages of simplicity and solidity. They interfere less 
with the accessibility of the boiler than through-stays or 
diagonal stays. Their chief defect is that they are very rigid 
and are apt to localize the springing of the flat plates, which 




Fig. 71. 

is caused by unequal expansion of the furnace-flues and shell. 
Consequently, grooving near gusset-stays is very likely to be 
found in Lancashire and Cornish boilers. Gusset-stays are 
also used to some extent in marine boilers, and in locomo- 
tive-boilers. 

Spherical Ends. — The ends of cylindrical boilers, or of 
steam-drums, are commonly curved to form a spherical sur- 
face, in which case they retain their form under internal 
pressure and do not need staying. If the radius of the 
spherical surface is equal to the diameter of the cylindrical 
surface, the same thickness of plates may be used for both. 
If the spherical surface has a longer radius, the thickness may 
be increased. Such dished heads of boilers and steam-drums 
are struck up between dies while at a flanging heat, and are 
then flanged to give a convenient riveting edge. 

Steam-domes are short, vertical cylinders of boiler-plate 
fastened on top of the shell of horizontal boilers. Plates II 
and III show steam-drums on locomotive-boilers. A steam- 
drum may be used to advantage when the steam-space is so 
shallow that there is danger that the ebullition may throw 



STAYING AND OTHER DETAILS. 171 

water into the pipe leading steam from the boiler. Locomo- 
tives usually have steam-domes, for not only is the steam- 
space shallow, but there is danger of splashing of the water 
in the boiler, especially if the track is rough or sharply 
curved. 

Stationary boilers ought to have steam-space enough with- 
out domes; marine boilers sometimes have domes, but they 
are less common than formerly. The additional steam- 
volume in a steam-dome is insignificant, so that a dome should 
not be added to increase steam-space of a boiler. 

The main objection to a steam-dome is that it weakens 
the boiler-shell, which must be cut away to form a junction 
with it. The shell may be reinforced, to make partial com- 
pensation, by a ring or flange of boiler-plate. Such a flange 
is clearly shown on Plate III, where the longitudinal seam of 
the ring carrying the dome is purposely placed at the top of 
the boiler. A similar arrangement is made for the dome on 
Plate II. 

Dry-pipe. — Any pipe inside of a boiler for the purpose of 
leading steam from the boiler is known as a dry-pipe; the 
pressure in such a pipe is frequently less than that of the 
steam in the boiler, consequently there is a tendency to dry 
the steam in the pipe. Dry-pipes are found in locomotive 
and marine boilers and sometimes in stationary boilers. 

The dry-pipe of a locomotive opens near the top of the 
dome. It runs vertically down till it is well below the shell 
of the barrel, then it runs horizontally through the steam- 
space and out through the smoke-box tube-sheet. The 
throttle-valve is at the inlet of the dry-pipe. It is controlled 
through a bell-crank lever by a rod which enters the head of 
the boiler from the cab. 

The marine boiler shown by Fig. 11 has a dry-pipe which 
is joined to a steam-nozzle at the front end of the boiler. 
This dry-pipe is pierced with numerous longitudinal slits on 



T72 



STEAM-BOILERS. 



the upper side; the sum of the area of such slits is seven 
eighths of the area through the stop-valve in the steam-pipe. 

Steam-nozzle. — The stationary boiler shown on Plate I 
has a cast-iron steam-nozzle at each end. The steam-pipe 
leading steam from the boiler is bolted to the rear nozzle, 
and the safety-valves are placed above the front nozzle. 

Nozzles are often made of cast steel. The best are forged 
without welds from one piece of steel. 

Manholes. — A manhole should be large enough to allow 
a man to pass easily inside the boiler. That on Plate I is 
fifteen inches long and eleven inches wide, and has its greatest 
dimension across the boiler. 

The manhole there shown is placed inside the shell of the 
boiler. Both the ring and the cover are forged from steel 
without a weld. Fig. 72 shows a form of manhole that is 




Fig. 72. 

placed outside the shell. This form is commonly made of 
cast iron, but cast steel manholes of similar form are used to 
some extent. 

The manhole-ring should be strong enough to give com- 
pensation for the plate cut away from the ring on which it is 
placed. 

The manhole-cover is placed inside the ring so that it is 
held up to its seat by the steam-pressure. The cover is 
drawn up to its seat by a bolt and removable yoke. Some- 



STAYING AND OTHER DETAILS. 173 

times there are two bolts each with its yoke. A cast-iron 
manhole naturally has a cast-iron yoke, and a forged manhole 
has a wrought-iron or steel yoke. 

The manhole-cover is made steam-tight by a rubber 
gasket; the form of the cover and its seat are such that the 
gasket cannot be blown out by the pressure of the steam. 

Hand-holes are provided at various places on boilers to 
aid in washing out and cleaning. Thus the boiler on Plate I 
has a hand-hole near the bottom at each end, and there are 
several hand-holes near the foundation-ring of the vertical 
boiler, shown by Fig. b. The hand-hole covers on Plate I are 
placed directly against the plate which is not reinforced. Each 
is held up by a bolt and a small yoke, which has a bearing on 
the plate completely round the hole. If the yoke has insuffi- 
cient bearing on the plate, the latter is liable to be damaged 
and leaks will occur. The hand-holes on the marine boiler 
shown by Fig. 11 are reinforced by small plates outside the 
boiler-heads. 

Washout Plugs. — Instead of hand-holes, washout plugs, 
two inches or two inches and a half in diameter, are provided 
near the corners of the foundation-ring of a locomotive fire- 
box. Such plugs are simply screwed into the outside plate 
of the boiler. Examples are shown by Plates II and III. 

Methods of Supporting Boilers. — Horizontal cylindrical 
boilers are commonly supported on the side walls of the brick 
setting, by brackets which are riveted to the shell of the 
boiler. Thus the boiler shown on Plate I has two such 
brackets on each side; this boiler is about sixteen feet long. 
If a boiler is as much as eighteen feet long, three brackets 
are used. The front brackets rest directly on the brickwork, 
but the other brackets rest on iron rollers, to provide for the 
expansion of the boiler. The brackets are set so that the 
plane of support is a little above the middle of the boiler. 

Fig. 73 shows a common form of bracket, made of cast 
iron, which is riveted to the shell above the flange of the 



174 



STEAM-BOILERS. 



bracket. A better form with rivets both above and below 
the flange is shown by Fig. 74. 











— \ 


00 



00 









t\ 













V ^ 


J 




I 


-tt 


000 



Fig. 73- Fig. 74. 

A detachable bracket, like that shown by Figs. 75 and 
76, may be used when the boiler must be put into a building 




@ ® © 



n v\ 



l\ 

l\ 
l\ 
\ 


\ 1 \ 




1 
1 

i 


1 


1 
1 




i^id : 







Fig. 75. 
through a small aperture. 



Fig. 76. 
Fig. 75 gives an end and side 



elevation and plan of the body of the bracket; Fig. 76 gives 





- - -T -— — - — 

— -V 



Fig. 77. Fig. 78. 

a side elevation and plan, with section, of the flange. After 
the boiler is in place the flange is thrust up into the dovetail 



STAYING AND OTHER DETAILS. 



/3 



groove in the body of the bracket. The pressure of the flange 
against the dovetail groove, intensified by the wedging action 
of the inclined sides, is liable to be excessive. To overcome 
this difficulty the bracket shown by Figs. 77 and 78 is often 




Fig. 79. 





1 


CO) 


i 




"6 ' 


\ 


I 









Fig. 81. Fig. 83. 

used. Fig. 77 shows the end elevation and a view from 
below, of a casting which is riveted to the shell. Fig. 78 
shows the same views of a casting which catches into the 
hollow under Fig. 77 and bears at the top against this same 
casting, the rivets bolting it to the shell being countersunk. 



176 



STEAM-BOILERS. 



Horizontal boilers, and especially plain cylindrical boilers, 
are sometimes hung from a support above the boiler, as shown 
by Figs. 79, 80, and 81. 

Fig. 79 shows a lug, made of boiler-plate, riveted to the shell 
of the boiler. The lugs are placed in pairs and the boiler is 
hung from these lugs by bolts that are supported between trans- 
verse beams over the boiler. Fig. 80 differs in substituting a 
loop for the lug. 

Fig. 81 shows a method of suspension with two short pieces 



^ 



m. 



± 



(2) 



_-&B 



Fig. 84. 



of plate above the lug, to give some flexibility and provide for 
expansion. 

Figs. 82 and 83 show methods of suspending a boiler from 
the top. These methods are proper only for boilers which have 
a small diameter. 

Whenever possible it is better to suspend a boiler rather than 
to support it by brackets. The top of a bracket comes 3 or 4 
inches below the longitudinal joint. If, due to any settlement of 
the brickwork, the bracket bears near its outer edge, there is a 
bending moment of considerable magnitude transmitted to the 
shell. 

This tendency to pull the shell out just at the bottom of the 
bracket and to push the shell in at the top of the bracket pro- 



STAYING AND OTHER DETAILS. 177 

duces very severe strains in boilers of large diameter and of great 
weight. 

Boilers over 20 feet long require three sets of supports. 

If brackets are used it is probable that the middle set will 
either take more or less than one third the weight. 

The proper way to support such a boiler is as shown in Fig. 84. 

Three lugs, like Figs. 79 and 80, or preferably like Fig. 81, 
are fastened to each side of the boiler. Rods from the front 
lugs pass up between two I-beams, resting on piers built up 
above the side walls of the setting, and fasten to the beams, as 
shown. 

Rods from the middle and rear lugs are attached on each side 
to an equalizer, which is in turn hung from I-beams in the same 
way as at the front. As these connections are free to turn the 
load is always distributed in the same proportion between the 
lugs. 



CHAPTER VIII. 
STRENGTH OF BOILERS. 

The determination of the thickness of boiler-plates, the 
size of stays, and other elements affecting the strength of a 
boiler, involves a knowledge of the properties of the materials 
used and a knowledge of the methods of calculating stresses 
in the several members of the boiler. A brief statement of 
these subjects, as applied to boilers, will be given here. 

Materials Used. — The materials used for making boilers 
are mild steel, wrought iron, cast iron, malleable iron, copper, 
bronze, and brass. 

In order to insure that materials used for making a boiler 
shall have the proper qualities, it is customary to require that 
specimens shall be tested in a testing-machine, and that they 
shall have certain definite properties, such as ultimate tensile 
strength, elastic limit, and contraction of area at fracture. 
In order that these properties shall be properly developed, it 
is essential that specimens shall be of right size and shape, 
and that the testing shall proceed in a correct method. 

Testing-machines. — The frame of a testing-machine 
carries two heads, between which the test-piece is placed, and 
to which it is fastened by wedges or other clamping devices. 
One head, called the straining-head, is drawn by screws or by 
a hydraulic piston, and pulls on the test-piece. The other 
head, called the weighing-head, transmits the pull to some 
weighing device. Boiler materials are commonly tested in a 
machine which has the pull applied by screws, driven through 
gearing by hand or by power; the pull is weighed by a system 
of levers and knife-edges, arranged like those of a platform 

178 






STRENGTH OF BOILERS. 1 79 

scale. Such a machine should be able to exert a pull of fifty 
or a hundred thousand pounds. 

Testing-machines that give a direct tension are commonly 
arranged to give also a direct compression. There are also 
machines arranged to give transverse loads, like the load 
applied to a beam. 

Forms of Test-pieces. - — A test-piece of boiler-plate 
should be at least one inch wide, planed on both edges, and 
should be about two feet long. A piece which is less than 
eighteen inches long is not fit for testing. 

Test-pieces eighteen inches to two feet long may be cut 
directly from bars or rods for making stays or bolts. Tf a rod 
is so large that the available testing-machine will not break- 
it, it is of course possible to turn it down to a smaller 
diameter, but it would be preferable to send such a rod to a 
machine that is powerful enough to break it at full size. 

Test-pieces of cast metal may be cast in the form of 
rectangular bars, which should be at least one inch wide and 
an inch thick. If the bars are rough or irregular it may be 
necessary to plane the edges, or perhaps to plane them all 
over. 

Test-pieces of boiler-plate should be cut from the edge 
of at least one plate of each lot of plates. Sometimes speci- 
fications require pieces from each plate used for a given boiler. 
Pieces should be cut from both the side and the end of a 
plate, for there is a grain developed by rolling either iron or 
steel boiler-plate, and tests should be made both with the 
grain and across the grain. 

Very hard material may require shoulders on the test- 
pieces to enable the testing-machine to get a proper hold. 
But iron or steel that is so hard as to require shoulders is 
much too hard for boiler-making; consequently there will be 
no reason for providing test-pieces of boiler iron or steel with 
shoulders. If test-pieces have shoulders, they should be at 
least ten inches apart. 



i8o 



S TEA M-B OILERS. 



Methods of Testing. 

□ 




-A test-piece of proper length is 
first measured to determine the 
breadth and thickness or else the 
diameter, as the case may be. 
A length of eight inches Is laid 
off near the middle of the test- 
piece, and clamps for measuring 
the stretch of the piece are ap- 
plied at the ends of this eight-inch 
length, as shown by Fig. 85. 
The piece is then secured in the 
machine and a load is applied. 
The distance between the clamps 
is now measured by a micrometer 
caliper with an extension-piece. 
The method of doing this is to 
place the head of the micrometer 
against a point on the flange of 
the clamp at one end, and adjust 
the length of the micrometer so 
that it shall just touch the cor- 
responding point on the other 
clamp. A little practice will en- 
able the observer to measure to 
one or two ten-thousandths of an 
inch.. As the load is increased 
the test-piece stretches, the in- 
crease of length being proportion- 
al to the increase of the load. The 
stretch is measured on both sides 
of the test-piece for each increase 
of load applied. If the test-piece 
is not straight or exactly aligned 
in the machine there may be some 
irregularity in the stretching at 






STRENGTH OF BOILERS. l8l 

first, but after a considerable load is applied the piece 
stretches uniformly until about half the maximum load that 
the piece can carry has been applied. During the progress 
of the test a point is reached beyond which the stretch in- 
creases more rapidly than the load; this is known as the 
elastic limit. 

After the elastic limit is reached the clamps are removed 
and the test proceeds without them, but at about the same 
rate of loading. A load is soon reached which the piece 
cannot permanently endure, shown by the fact that the scale- 
beam will fall though the straining-head remains at rest. 
This is called the yield point. The piece may, however, 
carry a considerably higher load if the straining-head is kept 
moving to take up the stretch. Finally, the piece begins to 
draw down rapidly, somewhere near the middle of its length, 
and when the piece breaks, the fracture shows about half the 
area of the piece before testing. Hard materials may draw 
down little, or not at all; the limit of elasticity may approach 
the strength of the material. 

The jaws or wedges of the testing-machine interfere with 
the stretching or flow of the material gripped by them. The 
influence of the wedges may extend two or three inches 
beyond their edge in the testing of boiler-plate. If a piece 
has shoulders they will have a like effect. Consequently the 
points at which a clamp is secured to a test-piece should be 
two or three inches from a shoulder or from the wedges of the 
machine. The wedges of a machine of a capacity of fifty or 
a hundred thousand pounds are four or five inches long. 
They will grip on three inches at the end of a test-piece, but 
not on less. The test-piece must have eight inches for 
measuring stretch, two or three inches at each end for flow, 
and three to five inches at each end in the wedges. Conse- 
quently the piece must be eighteen or twenty-four inches 
long. 

The method just described is slow and laborious, and. 



1 82 STEAM-BOILERS. 

requires two observers — one to measure stretch and one to 
weigh. For commercial work an automatic device is often 
used which registers loads and corresponding elongations. 
Such devices commonly record the yield point instead of the 
elastic limit; these two points should never be confused. 

Stress. — The number of pounds of force per square inch 
is called the stress. The stress is uniform on a piece under 
direct tension, and is equal to the load divided by the area of 
transverse section. Stress may be expressed in other units, 
such as tons per square foot or kilograms per square milli- 
meter. 

Strain. — The stretch of a piece, under direct tension, per 

unit of length is called the strain. If the original length is / 

a 
and the stretch is a, then the strain is — = s. 

The Limit of Elasticity is the limiting stress beyond 
which the strain increases more rapidly than the stress. The 
limit is not perfectly definite, and can be determined approxi- 
mately only. A load greater than the elastic limit will pro- 
duce an appreciable permanent elongation after the load is 
removed. A stress less than the elastic limit will produce 
only a slight permanent elongation; such elongation may be 
inappreciable. 

Yield Point. — The stress at which the scale-beam of a 
testing-machine will fall while the straining-head is at rest is 
called the stretch limit. 

Ultimate Strength. — The maximum stress that a piece 
will endure in a testing-machine is called the ultimate strength 
of the material. The strength depends somewhat on the rate 
of testing. The more rapidly the testing proceeds the higher 
will be the apparent strength. It is desirable that some 
standard rate of testing may be adopted by engineers so that 
results may be strictly comparable. 

The Modulus of Elasticity is the result obtained by 
dividing the stress by the strain. If the stress is/ pounds 






STRENGTH OF BOILERS. 1 83 

per square inch and the strain is s per inch, then the modulus 
of elasticity is 

E = t 

s 

Reduction of Area. — The area of the test-piece of boiler- 
plate at the rupture is much less than that of the piece before 
testing. This reduction is important, as it shows the ductility 
of the metal, and its ability to change shape without too 
much distress under the influence of unequal expansion of 
different members of a boiler. 

Ultimate Elongation. — After the test-piece is broken the 
two parts are laid down in a straight line with the broken 
ends in contact, and the length of the distance between the 
points of attachments of the measuring clamps is measured. 
The ratio of the elongation to the original length (eight 
inches) is called the ultimate elongation. The ultimate elon- 
gation is generally given in per cent. This is important, for 
the same reason given for the contraction of area. 

Compression. — The preceding definitions are given for 
tension only, for sake of simplicity and brevity; they may 
be applied to pieces in direct compression if the term stretch 
or elongation is replaced by compression. 

Shearing. — Stresses have thus far been considered to be 
at right angles to the sections of the pieces to which they are 
applied, and produce either tension or compression at that 
section. A stress that is not at right angles to a section will 
tend to produce sliding at that section. A stress that is 
parallel to a section will tend to produce sliding only, and is 
called a shearing-stress. If a shearing-stress is uniformly dis- 
tributed, its intensity may be found by dividing the total force 
or load by the area of the section. 

The rivets of a riveted seam are subjected to a shearing- 
stress. 



184 STEAM-BOILERS. 

Steel Specifications. — At the present time all boiler-plates 
are made of steel. 

The American standard specifications for steel of the American 
Society of Testing Materials are universally adopted in the United 
States. That part of the specifications relating to boiler and 
rivet steel will be quoted in full. 

OPEN-HEARTH BOILER PLATE AND RIVET STEEL. 

Adopted 1 901. 

Process of Manufacture. 

1. Steel shall be made by the open-hearth process. 

Chemical Properties. 

2. There shall be three classes of open-hearth boiler-plate 
and rivet steel; namely, flange or boiler steel, fire-box steel, and 
extra soft steel, which shall conform to the following limits in 
chemical composition : 

Flange or Fire-box Extra Soft 

Boiler Steel, Steel, Steel, 

Per Cent. Per Cent, Per Cent. 

_,. , , „ -j f Acid 0.06 Acid 0.04 Acid 0.04 

Phosphorus shall not exceed j Bask Q ^ Bask Q ^ b ^ q q £ 

Sulphur shall not exceed 0.05 0.04 0.04 

Manganese 0.30 to 0.60 0.30 to 0.50 0.30 to 0.50 

3. Boiler Rivet Steel. — Steel for boiler rivets shall be of the 
extra soft class as specified in paragraphs Nos. 2 and 4. 

Physical Properties. 

4. Tensile Tests. — The three classes of open-hearth boiler- 
plate and rivet steel — namely, flange or boiler steel, fire-box 
steel, and extra soft steel — shall conform to the following physical 
qualities: 

Flange or Fire-box Extra Soft 

Boiler Steel. Steel. Steel. 

Tensile strength, lbs. per sq. in. 55,000 to 65,000 52,000 to 62,000 45,000 to 55,000 

Yield-point, in lbs. per sq. in., 

shall not be less than JT. S. . JT. S. JT. S. 

Elongation, per cent in 8 inches, 

shall be not less than 25 26 28 



STRENGTH OF BOILERS. 185 

5. Modifications in Elongation for Thin and Thick Material. 
— For material less than five-sixteenths inch (5/16") and more 
than three-fourths inch (3/4") in thickness the following modi- 
fications shall be made in the requirements for elongation: 

(a) For each increase of one-eighth inch (1/8") in thickness 
above three-fourths inch (3/4") a deduction of one per cent (1%) 
shall be made from the specified elongation. 

(b) For each decrease of one-sixteenth inch (1/16") in thickness 
below five-sixteenths inch (5/ 16") a deduction of two and one- 
half per cent (2^%) shall be made from the specified elongation. 

6. Bending Tests. — The three classes of open-hearth boiler- 
plate and rivet steel shall conform to the following bending tests-: 
and for this purpose the test specimen shall be one and one-half 
inches (ij") wide, if possible, and for all material three-fourths 
inch (3/4") or less in thickness the test specimen shall be of 
the same thickness as that of the finished material from which 
it is cut, but for material more than three-fourths inch (3/4") 
thick the bending test specimen may be one-half inch (1 / 2") thick : 

Rivet rounds shall be tested of full size as rolled. 

(c) Test specimens cut from the rolled material, as specified 
above, shall be subjected to a cold bending test, and also to a 
quenched bending test. The cold bending test shall be made 
on the material in the condition in which it is to be used, and prior 
to the quenched bending test the specimen shall be heated to a 
light cherry-red, as seen in the dark, and quenched in water the 
temperature of which is between 8o° and 90 Fahrenheit. 

(d) Flange or boiler steel, fire-box steel, and rivet steel, both 
before and after quenching, shall bend cold one hundred and 
eighty degrees (180 ) flat on itself without fracture on the outside 
of the bent portion. 

7. Homogeneity Tests. — For fire-box steel a sample taken from 
a broken tensile test specimen shall not show any single seam or 
cavity more than one-fourth inch (1/4") long in either of the 
three fracutres obtained on the test for homogeneity as described 
below in paragraph 12. 



1 86 STEA M -BOILERS. 

Test-pieces and Methods of Testing. 

8. Test Specimen for Tensile Test. — The standard test speci- 
men of eight inch (8") gauged length shall be used to determine 
the physical properties specified in paragraphs Nos. 4 and 5. 

For other material the test specimen may be the same as for 
-sheared plates, or it may be planed or turned parallel throughout 
its entire length; and in all cases, where possible, two opposite 
sides of the test specimens shall be the rolled surfaces. Rivet 
rounds and small rolled bars shall be tested of full size as rolled. 

9. Number of Tensile Tests. — One tensile test specimen will 
be furnished from each plate as it is rolled, and two tensile test 
specimens will be furnished from each melt of rivet rounds. In 
case any one of these develops flaws or breaks outside of the 
middle third of its gauged length, it may be discarded and another 
Jest specimen substituted therefor. 

30. Test Specimens for Bending. — For material three-fourths 
inch (3/4") or less in thickness the bending test specimen shall 
have the natural rolled surface on two opposite sides. The 
bending test specimens cut from plates shall be one and one-half 
inches (ij") wide, and for material more than three-fourths inch 
(3/4") thick the bending test specimen may be one-half inch (1/2") 
thick. The sheared edges of bending test specimens may be 
milled or planed. The bending test specimens for rivet rounds 
shall be of full size as rolled. The bending test may be made by 
pressure or by blows. 

11. Number of Bending Tests. — One cold bending specimen 
and one quenched bending specimen will be furnished from each 
plate as it is rolled. Two cold bending specimens and two 
quenched bending specimens will be furnished from each melt 
of rivet rounds. The homogeneity test for fire-box steel shall 
be made on one of the broken tensile test specimens. 

12. Homogeneity Tests for Fire-box Steel. — The homogeneity 
test for fire-box steel is made as follows: A portion of the broken 
tensile test specimen is either nicked with a chisel or grooved on 



STRENGTH OF BOILERS. 187 

a machine, transversely about a sixteenth of an inch (1/16") 
deep, in three places about two inches (2") apart. The first groove 
should be made on one side, two inches (2") from the square 
end of the specimen; the second, two inches (2") from it on the 
opposite side; and the third, two inches {2") from the last, and 
on the opposite side from it. The test specimen is then put in a 
vise, with the first groove about a quarter of an inch (1/4") above 
the jaws, care being taken to hold it firmly. The projecting end 
of the test specimen is then broken off by means of a hammer, 
a number of light blows being used, and the bending being away 
from the groove. The specimen is broken at the other two grooves 
in the same way. The object of this treatment is to open and 
render visible to the eye any seams due to failure to weld up, 
or to foreign interposed matter or cavities due to gas bubbles in 
the ingot. After rupture, one sid£ of each fracture is examined, 
a pocket lens being used, if necessary, and the length of the 
seams and cavities is determined. 

13. Yield- point. — For the purpose of this specification the 
yield-point shall be determined by the careful observation of the 
drop of the beam or halt in the gauge of the testing-machine. 

14. Sample for Chemical Analysis.— In order to determine if 
the material conforms to the chemical limitations prescribed in 
paragraph 2 herein, analysis shall be made of drillings taken from 
a small test ingot. An additional check analysis may be made 
from a tensile specimen of each melt used on an order, other than 
in locomotive fire-box steel. In the case of locomotive fire-box 
steel a check analysis may be made from the tensile specimen 
from each plate as rolled. 

Variation in Weight. 

15. The variation in cross-section or weight of more than 
2 J per cent from that specified will be sufficient cause for rejection, 
except in the case of sheared plates, which will be covered by the 
following permissible variations: 



i88 



STEAM-BOILERS. 



(e) Plates 12^ pounds per square foot or heavier, up to ioo 
inches wide, when ordered to weight, shall not average more 
than 2 h per cent variation above or 2 h per cent below the theo- 
retical weight. When 100 inches wide and over, 5 per cent above 
or 5 per cent below the theoretical weight. 

(/) Plates under 12^ pounds per square foot, when ordered 
to weight, shall not average a greater variation than the following : 

Up to 75 inches wide, 2 h per cent above or 2 \ per cent below 
the theoretical weight. 75 inches wide up to 100 inches wide, 
5 per cent above or 3 per cent below the theoretical weight. 
When 100 inches wide and over, 10 per cent above or 3 per cent 
below the theoretical weight. 

(g) For all plates ordered to gauge, there will be permitted an 
average excess of weight over that corresponding to the dimen- 
sions on the order, equal in amount to that specified in the follow- 
ing table: 

Table of Allowances for Overweight for Rectangular 
Plates when Ordered to Gauge. 

Plates will be considered up to gauge if measuring not over 
1 /ioo inch less than the ordered gauge. 

The weight of 1 cubic inch of rolled steel is assumed to be 
0.2833 pound. 



PLATES 1/4 INCH AND OVER IN THICKNESS. 





Width of Plate. 


Thickness of Plate 








Inch. 


Up to 75 Inches. 


75 to 100 Inches. 


Over 100 Inches. 




Per Cent. 


Per Cent. 


Per Cent. 


1/4 


10 


14 


18 


5/l6 


8 


12 


16 


3/8 


7 


10 


13 


7/i6 


6 


8 


10 


1/2 


5 


7 


9 


9/16 


4} 


6* 


8* 


5/8 


4 


6 


8 


Over 5/8 


3* 


5 


6} 



STRENGTH OF BOILERS. 
PLATES UNDER 1/4 INCH IN THICKNESS. 



189 



Thickness of Plate. 
Inch. 


Width of Plate. 


Up to 50 Inches. 
Per Cent. 


50 Inches and Above. 
Per Cent. 


1/8 up to 5/32 
5/32 up to 3/16 
3/16 up to 1/4 


10 
Si 
7 


15 

IO 



Finish. 

16. All finished material shall be free from injurious surface 
defects and laminations, and must have a workmanlike finish. 



Branding. 

17. Every finished piece of steel shall be stamped with the 
melt number, and each plate and the coupon or test specimen 
cut from it shall be stamped with a separate identifying mark or 
number. Rivet steel may be shipped in bundles securely wired 
together with the melt number on a metal tag attached. 

Inspection. 

18. The inspector, representing the purchaser, shall have all 
reasonable facilities afforded to him by the manufacturer to 
satisfy him that the finished material is furnished in accordance 
with these specifications. All tests and inspections shall be made 
at the place of manufacture prior to shipment. 

Laminations. — The upper end of the ingot into which the 
molten steel from the open-hearth furnace is cast, is liable to be 
affected by bubbles and other imperfections when the ingot is 
poured from the top. Such imperfections, if they are not re- 
moved, give rise to lamination in the plates, and therefore when 
the ingot is rolled into blooms the crop end should be cut long 
enough to remove all the bubbles. There is always a tendency, 
on account of the reduction of prices through competition, to 



190 



STEAM-BOILERS. 



reduce the length of the crop end, and consequently steel plates, 
though having the other required physical properties, are liable 
to show lamination. 

It is to be noted that fire-box steel is better than flange steel. 

Blue Heat. — Steel plates, and other forms of mild steel, 
become brittle at a temperature corresponding, roughly, to a 
blue heat. A plate that will endure bending double, both 
hot and cold, is liable to show cracks if bent at a blue heat. 
In bending, flanging, and forging no work should be done on 
steel at a blue heat; properly, such work should be done at 
a bright red heat; work should never be continued after the 
steel becomes black. After the steel is cold it may be bent 
as readily as iron at the same temperature. 

Wrought Iron — All the stays and fastenings of boilers 
that are made by welding should be made of tough, ductile 
wrought iron. Welds made by a skilful smith may have as 
great a strength as the bar from which they are made. A 
ductile bar may break in the clear bar instead of in the weld, 
on account of the hardening due to the work done on the bar 
at the weld. It is customary to assume that 25 to 50 per 
cent of the strength of the bar may be lost by welding. 

Wrought-iron plates of a quality suitable for boiler-making 
are now more expensive than mild-steel plates, which are in 
every way as well adapted to the purpose, and which have a 
higher strength. Consequently we find wrought-iron plates 
used only when specially demanded. Wrought iron does not 
show cracks when worked at a blue heat, and in general may 
endure more abuse in working. This caused wrought iron 
to be preferred by many after reliable steel was produced 
cheaply, but boiler-makers now understand the working of 
steel plates and avoid improper handling. 

Wrought-iron plates should show a limit of elasticity of 
23,000 pounds, and a tensile strength of 45,000 pounds to 
the square inch. 






STRENGTH OF BOILERS. 191 

Wrought-iron rods and bolts should have a strength of 
48,000 pounds per square inch. 

Rivets. — The rivets used in boiler-making are either iron, 
or steel similar in quality to steel used for boiler-plates. 

A rivet should bend cold around a bar of the same 
diameter, and it should bend double when hot without frac- 
ture. The tail should admit of being hammered down when 
hot till it forms a disk 2\ times the diameter of the shank, 
without cracking. The shank should admit of being ham- 
mered flat when cold, and then punched with a hole equal in 
diameter to that of the shank, without cracking. 

The rods from which rivets are made should show a tensile 
strength of about 55,000 pounds for steel and about 48,000 
pounds for wrought iron. The other properties, such as 
ultimate elongation and contraction of area, should be like 
those for boiler-plate. 

The shearing strength of steel rivets is about 45,000 
pounds, and of iron rivets about 38,000 pounds; that is, the 
shearing strength will be between T V and y 8 o of the tensile 
strength. 

Cast Iron in different forms will show a tensile strength 
of 12,000 to 20,000 pounds to the square inch. Gun-iron, 
which is cast iron made with special care and skill from 
selected stock, has shown a tensile strength of nearly 30,000 
pounds to the square inch. In compression the strength of 
small pieces may be as high as 80,000 pounds to the square 
inch, but larger pieces, like columns, fail at 30,000 pounds 
to the square inch. 

Cast iron is used for some or all of the parts of sectional 
boilers, and for fittings such as manholes, though wrought 
iron is preferable for such purposes. Flat plates at the ends 
of cylindrical boilers are sometimes made of cast iron. 

In general, cast iron should never be used when it is sub- 
jected to severe changes of temperature or to stresses from 



192 STEAM-BOILERS. 

unequal expansion, and should be replaced by wrought iron 
or mild steel whenever it is practicable. 

Couplings, elbows, and other pipe-fittings are made of 
cast iron. The brittleness is a convenience when changes are 
to be made, as joints that cannot be opened are readily- 
broken. 

Malleable Iron, which is cast iron toughened by being 
deprived of part of the carbon, is used for pipe-fittings and for 
fittings of steam-boilers. It is used in place of cast iron for 
sectional boilers and for parts of water-tube boilers. Though 
tougher than cast iron, and though it will endure forging to 
some extent, its variability in quality and its unreliability 
prevent much reduction in weight and size when substituted 
for cast iron. 

Copper is largely used in Europe for making fire-boxes of 
locomotive-boilers and torpedo-boat boilers. Its greater cost 
is in part offset by the value of the scrap copper after the 
fire-box is worn out. 

Copper for fire-boxes, rivets, and stays should have a ten- 
sile strength of 34,000 pounds to the square inch, and should 
show an elongation of 20 to 25 per cent in 8 inches. It should 
not contain more than one-half per cent of impurities. The 
greater ductility of copper, and its greater thermal conduc- 
tivity, permitting of greater thickness for furnace-plates, 
recommends it to European engineers. 

Copper is largely used on steamships for making piping of 
all sorts, such as steam-pipes and water-pipes. Such pipes 
are made of sheet copper, rolled up or hammered to shape, 
scarfed and brazed at the edges. The pipe is also brazed to 
brass flanges for coupling lengths of pipe, or for joining to 
steam-chests or other parts of the engine or boiler. If the 
brazing is not done with care and skill the brazed joint may 
lose as much as half the strength of the sheet copper. Several 
disastrous explosions of such piping have occurred. Conse- 






STRENGTH OF BOILERS. 1 93 

quently wrought-iron piping is finding favor for high-pressure 
steam. 

Bronze and Composition. Brass. — Bronze is properly 
an alloy of copper and tin; thus gun-metal is 90 parts of 
copper to 10 of tin. Compositions of various qualities are 
made of copper and zinc with more or less tin. Brass is an 
alloy of copper and zinc; for example, brass smoke-tubes are 
made of 70 parts of copper to 30 parts of zinc. Lead is 
added to brass and to composition to reduce the cost and to 
make the metal work easier. It may be considered as an 
adulteration, as it cheapens the metal at the expense of the 
quality. There are many special bronzes, such as phosphor- 
bronze and aluminium-bronze, which are used for special 
purposes. 

Brass is used to some extent for smoke-tubes of locomo- 
tive and other boilers, on account of its greater thermal con- 
ductivity, by European engineers. In America, brass is used 
for valves, gauges, and other boiler fittings. Composition or 
bronze is advantageously used for the valves and seats of 
safety-valves and wherever the service endured is excep- 
tionally hard. Brass is more commonly used because it is 
cheaper. In a general way it may be said that the cost and 
quality of brass and composition is proportional to the copper 
it contains; thus red brass is better and costs more than 
yeliow brass. Many small brass fittings on the market are 
sold at a price which precludes the use of proper alloys, and 
they are consequently soft and worthless. 

Stay-bolts are usually arranged in equidistant horizontal 
and vertical rows; as an example we may take the stay-bolts 
in the locomotive fire-box on Plate II. These bolts are 7/8 
of an inch in diameter outside of the threads, and are spaced 
4 inches on centres. The total load on each stay-bolt with 
a steam-pressure of 170 pounds to the square inch is 

4 X 4 X 170 = 2720 pounds. 



194 STEAM-BOILERS. 

The diameter of the bolt at the bottom of the screw-thread 
is about 0.7 of an inch, and the area of the section is about 
0.4 of a square inch. The stress is consequently 

2720 ~ 0.4 = 6800. 

Sometimes the area is calculated from the external diam- 
eter of the bolt, a proceeding which may lead to a gross error. 
In the present instance the corresponding area is about 0.6 
of a square inch, which gives an apparent stress of about 
4500. 

Suppose that the thread is turned off from the body of 
the bolt, and that the diameter is thereby reduced to 5/8 of 
an inch. The area of the section is then about 0.3 of an 
inch, and the stress is 

2720 -f- 0.3 = 9000 -f-. 

The stress on stay-bolts should always be low to allow 
for wasting from corrosion, and to allow for unknown addi- 
tional stresses that may be caused by the unequal expansion 
of the plates that are tied together by the stay-bolts. 

Stay-rods. — Through-stays like those passing through the 
steam-space of the marine boiler, shown by Fig. n, page 17, 
are treated much like stay-bolts. Thus the stays in question 
are 14 inches apart horizontally and 13 inches apart vertically. 
If they are each assumed to support a rectangular area 13 
inches wide and 14 inches long, the total force from 160 
pounds steam-pressure will be 

14 X 13 X 160 = 29120. 

The diameter of these stays in the body is 2 inches, which 
gives an area of section of 3.14 square inches. The stress is 
consequently 

29120 -^ 3.14 = 93 00 



STRENGTH OF BOILERS. 



r 95 



These stay-rods have swaged heads on which the screw- 
thread is cut, so that the diameter at the bottom of the 
thread is greater than the diameter of the body. 

Stay-rods which are used in connection with girders, as on 
Plate I, will have to carry loads which depend on the surface 
supported, the steam-pressure, and the number and arrange- 
ment of the stays. The determination of the load may be 
difficult and uncertain, but the calculation of the stress for a 
given load is very simple. 

Diagonal Stays. — If a stay-rod runs diagonally from a 
flat plate to the shell of a boiler, it will evidently be subjected 

/ 




Fig. 86. 
to a greater stress than it would be if it were a through-stay. 
Thus in Fig. 86 we have at the point a the parallelogram of 
forces abed; ab is the total pressure supported by the stay, ac 
is the pull on the stay, and ad is a force that must be taken 
up by the flat plate. But the triangles abc and aef are simi- 
lar, so that we have 



ac 

ab 



af_ *V + ef 
ef ~ ef 



Suppose, for example, that ae is two feet and ef is six 
feet; then 



ab ~~ 6 



= 1-054, 



196 STEAM-BOILERS. 

or the pull on the stay is more than five per cent in excess of 
what a through-stay would be required to support. 

Gusset-Stays are open to the defect that the distribu- 
tion of stress on the plate forming the stay is uneven and 
uncertain. It is customary to calculate them on the assump- 
tion that the resultant stress acts along /* \ 
a medial line, and is evenly distributed / \ 
over a section at right angles to that line. / \ 
A low apparent working-stress should be [ — j 
used. \ I 

Thin Hollow Cylinder. — Let Fig. 

87 represent a semicircular steam-drum ^>- --" 

closed at the bottom by a thick flat plate. FlG * 8 ?- 

If the steam-pressure is p pounds per square inch, the radius 

is r, and the length is /, then the pressure on the plate is 

2prl. 

If the thickness of the cylinder is t, and the stress per 
square inch on the metal of the cylinder is s, then the pull of 
the cylinder at one end of the plate is 

stl. 

But this must be equal to half the pressure on the plate, 
so that 

stl = prl. 

:■..-$ 

For safety the stress should not exceed the safe working 
stress for the material of which the cylinder is made ; so that 
we have 

/-* 






STRENGTH OF BOILERS. 197 

It is evident that the pull on the side of the cylinder and 
the stress per square inch will be the same if another half- 
cylinder is substituted for this plate, making a complete thin 
hollow cylinder. 

Example I.- — A thin hollow cylinder five feet in diameter 
and half an inch thick, working at a pressure of 200 pounds, 
will be subjected to a stress of 

5 X 12 
200 X '- i = 12,000 

pounds per square inch. If the cylinder is made of one con- 
tinuous plate of steel without longitudinal joint, this stress 
will be about one fifth of the ultimate strength. 

Example 2. — If it is desired that the stress shall be 9000 
pounds in a cylinder 9 feet in diameter when exposed to a 
pressure of 120 pounds to the square inch, then the thickness 
of the plate should be 

pr 9 X 12 
t = —z = 120 X -7- 9000 = 0.72 

of an inch. 

End Tension on a Cylinder. — In the preceding cylinder 
we have considered the tension on a section at the side of the 
cylinder. Let us now consider the tension on a transverse 
section. 

If the cylinder is closed by a flat plate at the end, the 
area of that plate will be 

3.1416?- 2 , 

and the total force due to a pressure of p pounds per square 
inch will be 

3.1416^. 



1 98 STEA M-BOILERS. 

This force will be resisted by a ring of metal having a cir- 
cumference 2 X 3.1416?-, and a thickness t. The resistance 
of the ring will be 

2 X 3.1416;-/*, • 

representing the stress by s. Consequently we shall have 
2 X 3- J 4i6r^ = 3. 1416;-'/. 

2t 

It is evident that the stress from the end pull is half the 
stress on the section at the side of a cylinder, and conse- 
quently a cylinder made of homogeneous material without 
joints will always be ruptured longitudinally. 

It is also evident that the stress from the end pull will be 
the same if the end of the cylinder is closed by a spherical 
surface, or by any other figure, instead of a flat plate. 

Thin Hollow Sphere- — A section taken through the cen- 
tre of a sphere is in the same condition as a transverse sec- 
tion of a thin cylinder, and will be subjected to the same 
stress, if the sphere has the same thickness and is subjected 
to the same internal pressure. 

Formerly the ends of plain cylindrical boilers were made 
hemispherical, but such* ends are difficult to make and are 
needlessly strong if of the same thickness as the cylindrical 
shell. It is now the practice to curve such ends to a less 
radius than that of the cylindrical shell. If the radius of the 
head is equal to the diameter of the shell, then with the same 
thickness of plate the stress will be the same per square inch, 
provided there are no seams in head or shell. The heads 
usually do not have a seam, and the shells always have a 
seam ; the margin of strength in the head, when the same 
thickness of plate is used, under this condition may be offset 
against the possible injury done to the head in shaping it. 



STRENGTH OF BOILERS. 



199 



The construction known as a bumped-np head has the 
edge flanged into a cylindrical form to make a joint with the 
shell, and to avoid the awkward stress that would be thrown 
onto the cylindrical shell if the true cylindrical and spherical 
surfaces were allowed to intersect. 

If it is inconvenient to curve the head to a radius as small 
as the diameter of the cylinder, then a thicker 
plate may be used, with a longer radius. 

Rivets. — The plates of a boiler are joined at 
the edges by rivets ; rivets are also used in stays 
and other members. 

The usual form of rivets is shown by Fig. 
88. If the diameter of the rivet is D, then the 
proportions may be 



e=s 




D 

B 
D 



= 1.4 



= 1.2; 



C 
D 



0.7 ; 



D = 3/4 ' 



The length of the rivet will depend on the number and 
thickness of the plates through which it is to pass. 

The rivet represented by Fig. 88 has a pan head. Of the 
rivets shown by Fig. 89, A, B, and C have pan heads, and D 
and E have round or hemispherical heads. 

The form of the point of a rivet will depend on the way 
in which the rivet is driven and on the shape of the tools or 
dies used for forming the point. The rivet A has a straight 



200 



STEAM-BOILERS. 



conical point ; this is the only form that can be made when 
the rivet is driven by hand with flat-faced hammers. 

The rivet B has the head formed by a die or snap. The 
rivet is driven by a few heavy blows of a hammer, and the 
head is roughly formed; then a die or snap is placed on the 
point and driven to form the point by a sledge-hammer. 

C shows a rounded conical point commonly used for 
machine-driven rivets. The heads of such rivets may have a 
similar form. 

D represents the usual form of countersunk rivets: the 
hemispherical head is not a peculiarity of such rivets; it is 




Fig. 89. 



occasionally used with any form of point. The rivet E has 
some fulness or projection at the point beyond the counter- 
sink. 

After a rivet is driven, both ends are called heads; the 
distinction of heads and points is made here for convenience 
in description. 

The straight conical form A is liable to be too flat and 
weak. Its height should be three-fourths the diameter of 
the rivet. 

When rivet-holes are punched in plates they are slightly 
conical, as shown by B, Fig. 89, which shows the two smaller 
ends of the rivet-holes placed together to facilitate the proper 
filling of the hole by the rivets. The other rivet-holes are 
straight, as they would be if drilled. 



STRENGTH OF BOILERS. ?oi 

Riveted Joints. — The proportions of riveted joints, such 
as diameter and pitch of rivets, are determined in part by- 
practice and in part by a method of calculation to be explained 
later. In practice it is found necessary to limit the pitch of 
the rivets, and consequently the diameter, to be used with a 
given thickness of plate, in order that the joint may be made 
tight by calking. This limitation frequently makes the joint 
weaker than it otherwise would be. 

The edges of plates are either lapped over and rivetec', or 
brought edge to edge and then joined by a cover-plate which 
is riveted to each of the two plates. The first method makes 
a lap-joint and the second a butt-joint. 

Fig. 90 shows a single-riveted lap-joint and Figs. 91 and 92 
show double riveted lap-joints. The rivets in Fig. 91 are said 
to be staggered; the form shown by Fig. 92 is called chain-rivet- 
ing. 

Butt-joints with two cover-plates are shown by Figs. 95, 96, 
and 97. The outer cover-plate is narrow, with rivets placed close 
enough together to provide for sound calking. The inner plate 
is wider, and as its edges are not calked they may have a row of 
more widely spaced rivets. These joints, and those shown by 
Figs. 93 and 94, are designed with the view of securing more 
strength than can be had with a plain lap-joint like Fig. 91, or 
than can be had with a butt-joint with cover-plates of equal 
width. 

Efficiency of a Riveted Joint.— The strength of a riveted 
joint is always less than that of the solid plate, because some of 
the plate is cut away by the rivets. This is very evident in the 
case of a single-riveted joint, such as that shown by Fig. 90; it 
will be found to be true for more complicated joints, such 
as those shown by Figs. 95, 96, and 97. The efficiency 
of a riveted joint is the ratio of the strength of the joint to the 
stength of the solid plate. 

The strength and efficiency of a given riveted joint can be 



202 STEAM-BOILERS. 

properly determined only by direct test on full-sized speci- 
mens, which have considerable width. Tests on narrow 
specimens are liable to be misleading. Tests on boiler-joints 
are expensive, and can be made only on large and power- 
ful testing-machines. Tests have been made on behalf of 
the United States Navy Department at the Watertown 
Arsenal on a large number of single-riveted joints, on a con- 
siderable number of double-riveted joints, and on a few 
special joints. A few tests have been made elsewhere on full- 
sized joints. These tests give us important information that 
can be used in designing joints for boilers, but we cannot in 
general select a joint directly from the tests. 

Methods of Failure. — A riveted joint may fail in one of 
several methods, depending on the proportions, such as thick- 
ness of plate and the diameter and pitch of the rivets. This 
can be clearly seen in case of a single-riveted joint like that 
shown by Fig. 90. Such a joint may fail: 

(1) By tearing the plate at the reduced section between the 
rivets. If the rivets have the diameter^ and the pitch /, 
then the ratio of the area of the reduced section to that of 
the whole plate is 

p - d 
P 

(2) By shearing the rivets. 

(3) By crushing the plate or the rivets at the surface where 
they are in contact. 

(4) By cracking the plate between the rivet-hole and the 
edge of the plate, or by some method of failure due to in- 
sufficient lap. A riveted joint never fails by this method in 
practice, because the lap can always be made sufficient. 

The failure of more complicated joints may occur in 
various methods, which will be considered In connection with 
the calculation of some special joints. 






STRENGTH OF BOILERS. 203 

Drilled or Punched Plates. — In the better class of boiler- 
shops it is now the practice to drill rivet-holes in plates after 
the plates are in place, so that the holes are sure to be fair. 
Sometimes the holes are punched to a smaller diameter and 
then drilled out to the final size after the plates are in place. 
The result is the same as though the holes were drilled in the 
first place, as the metal near the hole, which was injured in 
punching, is all removed. The metal remaining between 
drilled holes does not have its properties changed by the 
drilling. On the contrary, the metal between punched holes 
is always injured more or less. In general, soft ductile metal 
is injured less than hard metal, and further, soft-steel plates 
are injured less than wrought-iron plates. 

When boiler-plates are punched and then rolled to form 
cylindrical shells, some of the holes are liable to come unfair, 
so that a rivet cannot be passed through. In such cases the 
holes should be drilled to a larger size, and a rivet of corre- 
sponding diameter should be substituted. Careless or reck- 
less workmen sometimes drive in a drift-pin, and stretch or 
distort the unfair holes so that a rivet can be forced through. 
The plate is liable to be severely injured by such treatment, 
and the rivet cannot properly fill the rivet-holes. Unfortu- 
nately it is difficult or impossible to detect bad work of this 
kind after the rivets are driven. 

Tearing. — The metal between the rivet-holes in a riveted 
joint cannot stretch as a proper test-piece does in the testing- 
machine, and consequently it shows a greater tensile strength 
than a test-piece from the same plate. Some tests on single 
or double riveted joints with small pitches show an excess 
of strength from this cause, amounting to ten per cent or 
more. The excess appears to be uncertain and irregular, so 
that if any allowance is made for it, it should be by a skilled 
designer after a careful study of all the tests that have been 
made. Ordinarily it will be safer to use the tensile strength 
shown by test-pieces in the testing-machine, especially for joints 
like Fig. 93, which have a large pitch for some of the rivets. 



204 STEAM-BOILERS. 

Shearing. — In general it is fair to assume the shearing 
strength of rivets of iron or steel to be between T 7 o and & of the 
tensile strength of the metal from which the rivets are made. 

Crushing. — It is customary to assume that the pull on a 
riveted joint is evenly distributed among the rivets in the 
joint, and to divide the total pull by the number of rivets to 
find the shearing or crushing force acting on one rivet. It is 
further customary to assume that the intensity of the crushing 
force on the surface where the rivet bears on the plate, may 
be found by dividing the total force on one rivet, by the 
product of the diameter of a rivet and the thickness of the 
plate. 

The crushing-stress on rivets in joints that fail by crushing 
is found by experiment to be high and irregular. In some 
cases it has amounted to 150,000 pounds per square inch; in 
a few tests it is less than 85,000 pounds. It is probable that 
95,000 pounds may be used with safety in calculating riveted 
joints for boilers. Now the stress on the bearing-surface 
will seldom be so much as one third the ultimate strength, 
even during a hydraulic test of a boiler, and it is not probable 
that a joint will be injured in this way unless the stress 
approaches the ultimate strength. 

Friction of Riveted Joints. — It is evident that there must 
be considerable friction between plates that are firmly clamped 
together by rivets driven hot. It has been proposed to take 
some account of this friction in calculating riveted joints, or 
even to allow the friction to be the determining element in 
proportioning riveted joints. Such a method is shown by 
experiment to be unsafe, for slipping takes place at all loads, 
beginning at loads that are much smaller than a safe load, and 
the effect of friction disappears before a breaking load is 
reached. 

L a p. — The distance from the centre of the rivet-hole to 
the edge of the plate is called the lap. The lap is usually 
once and a half the diameter of the rivet, a proportion that 
appears to be satisfactory. 






STRENGTH OF BOILERS. 



205 



Diameter of Rivet. — The minimum diameter of punched 
holes is determined by the consideration that the punch 
should not be broken. In the ordinary methods of punching 
boiler-plates the diameter of the punch should at least be as 
much as the thickness of the plate. It very commonly is 
once and a half the thickness of the plate. 

Drilled rivet-holes may have any diameter. They never 
have a diameter less than the thickness of the plate. The 
maximum diameter of rivet to be used with any kind of 
riveted joint will in general be determined by the considera- 
tion that the tendency to crush the plate in front of the rivet 
should not be greater than the shearing strength of the rivet. 
The maximum diameter thus found is liable to give too large 
a pitch. 

Pitch. — The maximum pitch for a given plate along a 
calked edge should be determined by the consideration that 
the plate should be held up rigidly enough to make a tight 
joint without excessive calking. The pitch of rivets, like 
those in the outer row of the joint shown by Fig. 78, need 
not be governed by this rule. There does not appear to be 
any explicit rule deduced either from practice or experiment 
for determining the proper pitch of rivets. 

Single-riveted Lap-joint. — In the joint shown by Fig. 90 

let the thickness of the plate be /, the 

diameter of the rivet d y and the pitch 
p, all in inches. Let the tearing 
strength of the plate be f t = 55,000, 
the shearing strength be /, = 45,000, 
and the resistance to crushing be 
f c — 95> 000 > a ^ f° r mild steel. 
Assume the proportions 

Fig. 90. df= 15/16, t=?/l6, p = 2%, 

It will be sufficient to consider a portion of the plate 
having a width equal to the pitch. The failure of such a strip 
may occur in one of three ways : 



.1 



206 STEAM-BOILERS. 

1st. Shearing o?ie rivet. The area to be sheared is 

4 

X T A I f)d^ 

or _J # The resistance to shearing is found by multi- 

4 
plying this area by the shearing strength of the rivet : 

nd\ n X 15 X 15 X 45, 000 

T" /s = 4 x i6>TT6- = 3I '° 63 * 

2d. Tearing plate between rivets. The effective width of 
the strip under consideration, allowing for the rivet-hole, is 
p — d, and the thickness of the plate is / ; the resistance to 
tearing is 

(P - d)tf t = (2i - i|) T V X 55,ooo = 31,580. 

3d. Crushing of rivet or plate. The conventional method 
is to assume the effective bearing area to be equivalent to the 
diameter of the rivet multiplied by the thickness of the plate. 
The resistance is considered to be 

dt fc = H X A X 95,000 = 38,970. 

The strength of a strip of the plate 2} inches wide is 

2{X T \X 55,ooo= 54,140. 

The calculated resistance to shearing is less than the 
resistance to tearing or compression. The apparent effi- 
ciency of the joint is 

31,063 
100 x 77T^ = 57-4 P^ cent. 
54, l 4° 

If it oe assumed that the resistance to tearing of the 
section between rivets will have an excess of ten per cent 
over the resistance of a piece in a testing-machine, then the 
resistance to tearing between rivets will appear to be 34,740 
This figure is not far from the resistance to shearing, though 
still inferior. If it be further assumed that the whole plate 



STRENGTH OF BOILERS. 



207 



outside of the joint will show a tearing strength of only 
55,000 pounds per square inch, the efficiency of the joint will 
appear to be more than five per cent greater than that given 
above. It is probably wise to ignore the excess of strength 
due to the fact that the plate between the rivets will not 
draw down for reasons that have already been stated at length. 
Double-riveted Lap-joint. — The rivets in this joint may 
be staggered as shown by Fig. 91, or chain-riveting may be 





Fig. 91. 

used as in Fig. 92. If the rivets are staggered and the two 
rows are too near together, it is possible that the plate may 




Fig. 92. 



tear down from a rivet in one row to the nearest rivet in the 
next row, and thus have, after tearing, a jagged edge. With 
the usual proportions such a failure will not occur, but the 
plate will tear between rivets in the same row, if it fails by 



208 STEAM-BOILERS. 

tearing. The calculation for efficiency will consequently be 
the same for both methods of riveting. 

Let the dimensions be 

/ = 7/16, d = 13/16, p = 2i. 

The joint may fail in one of three ways: 

1st. Shearing two rivets. The assumed strip having a 
width equal to the pitch will be held by two rivets ; this is 
apparent at once for chain-riveting. For staggered rivets 
such a strip will contain one whole rivet and half of two 
others, so that the same rule holds. The resistance of two 
rivets to shearing will be 

2nd 2 . £ r ~ 

/, = 46,660. 

4 

2d. Tearing between two rivets. The resistance is 

(p — d)tf = 40,600 

3d. Crushing in front of rivets. Just as for shearing, we 
have here the resistance at two rivets equal to 

2dtf= 67,540. 

The strength of the plate for a width of the pitch is 

ptf = 60, 160. 

The plate will apparently fail by tearing, and the effi= 
ciency of the joint will be 

40,600 ^ 
100 X ^- L — f~ — 67.5 per cent. 
60,160 

The increase of efficiency of the double-riveted lap-joint 
over the single-riveted joint is clearly due to reducing the 
diameter of the rivet and increasing the pitch. A further 
increase of efficiency could be obtained by using three rows of 
rivets ; this, however, is practicable only for thick plates, as 
we are liable to get too wide a pitch for sound calking. 

Single-riveted Lap-joint, Inside Cover-plate In this 

joint the plates are lapped and joined by a single row of rivets; 



STRENGTH OF BOILERS. 



209 



and a plate is worked inside and riveted through the shell 
with a single row of rivets, which are spaced twice as far apart 
as the rivets in the lap. In making up the joint all three rows 
of rivets may be driven at the same time. The lapped joint 
only is calked ; the pitch of rivets through the lap must con- 
sequently be small enough to give sound calking. The outer 
rows of rivets are not controlled by this rule. 

We will here consider a strip having the width a, Fig. 93, 
equal to twice the pitch of the rivets in the lap. Such a strip 
will be held by two rivets in the lap and by one rivet in an 
outer row. 

Assume the following dimensions: 

Thickness of shell and of cover-plate, t = 5/16. 

Diameter of rivets (iron), d = 3/4. 

Pitch of rivets in lap, p — \\. 

Pitch of outer rows of rivets, P= 3 J. 

Shearing resistance of iron rivets per square inch or f s = 
38,000 lbs. 

The joint may fail in one of five ways: 





jo c 


> c 


> ©" 


loot 


)OC 


bo p o 


1 






--.-.... 





c 


>"K 


) 






J 



Fig. 93 
1st. Tearing between outer row of rivets. The resistance I 
(P-d)tf t = 47,270. 



2IO STEAM-BOILERS. 

2d. Teari?tg between inner row of rivets, and shearing 
outer row of rivets. The resistance is 

4 

Since the rivets are iron, f s = 38,000. 

3d. Shearing three rivets. The resistance is 

3 nd* - 
4 

4th. Crushing in front of three rivets. The resistance is 
3tdf = 66,800. 

5 th. Tearing at inner row of rivets and crushing in front 
of one rivet in outer row. The resistance is 

(P-2d)tf t + tdf = 56,641. 

The strength of a strip of plate 3J inches wide is 

Itf — 60,160. 

The least resistance is offered by the first method, giving 
for the efficiency 

47,270 
160 X 60,160 = ;8,6 per cent ' 

If the inside cover-plate is thinner than the shell, addi- 
tional complication will be introduced into the calculations 
for resistance. 

Double-riveted Lap-joint with Inside Cover-plate. — 
The arrangement of this joint is shown by Fig. 94. Assume 
the dimensions: 

Thickness of shell and of cover-plate, t = 7/16. 

Diameter of rivets (steel), d = 3/4. 

Pitch of rivets in lap, 2-J-f. 

Pitch of outer rows of rivets, P = 4. 



STRENGTH OF BOILERS. 

The methods of failure are: 

1st. Tearing at outer rozv of rivets. 

Resistance (P — d)tf t = 78,210. 
2d. Shearing four rivets. 

47td 2 
Resistance f = 79,56c. 



211 




Fig. 94. 

3d. Tearing at inner rozv and shearing outer row of rivets, 
A strip having the width of the pitch of the outer row of 
rivets will be weakened at the rivets in the lap to the extent 
of one rivet-hole and half another rivet-hole. The resist- 



ance is 



nd" 
(P- \\d)tf + —f = 89,080. 



4th. Crushing in front of four rivets. 

Resistance 4tdf = 124,640. 

5th. Tearing at inner row of rivets and crushing in front 
of one rivet. 

Resistance (P - i\d)tf + tdf = 100,350. 






212 STEAM-BOILERS. 

Strength of strip 4 inches wide, 
Ptf t =96,250. 
Efficiency = ioo X / =81.3 per cent. 

Double-riveted Butt-joint. — The joint shown by Fig. 
95 has a cover-plate inside and another, narrower, outside. 
There are two rows of rivets on each side of the joint. The 
inner rows are nearer together and pass through both cover- 
plates. 




Fig. 



95- 



The outer row of rivets are wider apart and pass through 
the inner cover-plate only. 

The dimensions assumed are: 

Thickness of the plate and of both cover-plates, / = 7/16. 

Diameter of rivets (iron), 15/16 inch. 

Pitch of inner row of rivets, 2J . 

Pitch of outer row of rivets, 5J. 

There are five ways in which the joint may fail : 
1st. Tearing at outer row of rivets. The resistance is 

(P- d)tf t = 103,770. 



STRENGTH OF BOILERS. 2 1 3. 

2d. Shearing two rivets in double shear and one in single 
shear. If the plate pulls out from between the cover-plates 
shearing off the rivets, then the rivets in the inner row must 
be sheared through on both sides of the plate, or they are in 
double shear. The outer row of rivets are sheared at only one 
place. There are, consequently, five sections of rivets to be 
sheared for a strip as wide as the larger pitch. The resist- 
ance is 

~--f s = 131,100. 
4 

3d. Tearing at inner rozv of rivets and shearing one of the 
outer row of rivets. The resistance is 

(P -2d)tf t + *—f, = 107,430. 

4th. Crushing in front of three rivets. The resistance is 

pdf = 116,880. 

5 th. Crushing in front of tzuo rivets and shearing one 
rivet. The resistance is 

7td* 

2tdf + — /, = 104, 140. 
4 

The strength of a strip 5J inches wide is 

Si X T \ Xf t = 126,560. 

The efficiency is 

103,770 
100 — 7 — -z- — 82 per cent. 
126,560 r 

Triple-riveted Butt-joint. — The joint shown by Fig. 96 
has three rows of rivets on each side. Two rows pass through 
both cover-plates, and the third or outer row passes through 
the inner cover-plate only. 



2J4 



STEAM-BOILERS. 



The dimensions are: 

Thickness of shell, / = 7/16. 
Thickness of both cover-plates, t c = 3/8. 
Diameter of rivets (steel), d— 15/16. 
Pitch, inner rows, / = 3|. 
Pitch, outer row, P = J\. 



r^ 


,..._. ■ 1 


\ ? 


T^ r> (?'. 


\ (T*\ 


1 A^ l %j w 


© O p O 1 O O 

<j> 6^ 9 


c 




) c 




) O O 
O O 


c 


\ - a - -f 


> O 


\J * ^ 


I . 


' ) 



Fig. 96. 

The joint may fail in one of five ways: 

1st. Tearing at outer row of rivets. The resistance is 

(P-d)tf t = 151,890. 

2d. Shearing four rivets in double shear and one in single 
shear. The resistance is 

97td\ 

-7-/.= 279.450. 
4 

3d. By tearing at middle row of rivets (zuhere the pitch is 
3j- inches) and shearing one rivet. The resistance is 

(P- 2d)tf + U —f s = 160,340. 



STRENGTH OF BOILERS. 215 

4th. By crushing in front of four rivets and shearing 
one rivet. The resistance is 

nd* 

4dtf c -f / = 186,830. 

4 

5th. By crushing in front of five rivets. Four of these 
rivets pass through both cover-plates and will crush at the 
shell-plate. The fifth rivet passes through the inner cover- 
plate only, and will crush at that plate, since the cover-plates 
are thinner than the shell-plate. The resistance is 

4-dtf -\- dt c f c = 189, 170. 

The strength of a strip of plate 7J inches wide is 

Ptf= 174,370. 

The efficiency is 

151,890 

100 X — = ^>7 per cent. 

174,370 

Quadruple Riveted Butt-joints with two cover-plates. 
Fig. 97 shows such a joint. 

Thickness of shell, t = iJ2 inch. 

Thickness of both cover-plates, t c = j/i6 inch 

Diameter of rivets (steel), d = 15/16 inch. 

Pitch of inner row, p = $i inches. 

Pitch of second row, p = si inches. 

Pitch of third row, P = 7 h inches. 

Pitch of outer row, P = 15 inches. 
The joint may fail in one of eight ways: 
15/. Tearing at the outer row of rivets. The resistance is 

(P-d)# = 3 86,7oo. 

2d. Tearing at the third row and shearing one rivet in the 
outer row. The resistance is 

Tld 2 

(P — 2d)tf t H /« = 400,410. 

4 






2l6 



STEAM-BOILERS. 



yl. Tearing at the second row of rivets and shearing three 
rivets. The resistance is 



-d 2 
(P - 4d)tft + 3 —f 8 = 402,560. 




Fig. 97. 

4th. Double shearing eight rivets and single shearing three. 
The resistance is 

19— -/, = 590,200. 



$th. Crushing in front of eight rivets and single shearing three. 

The resistance is 

Tid 2 
Utf c + 3—-/* = 449>44Q. 



STREXGTH OF BOILERS. 21 7 

6th. Crushing in front of eleven rivets. The resistance is 

1 idtf c = 489,840. 

yth. Tearing at the third row of rivets and crushing in front 
of one rivet in the outer row. The resistance is 

(P-2d)tft+dtf c = 413,880. 

8th. Tearing at the second row of rivets and crushing in front 
of three rivets. The resistance is 

(P- 4 d)tf + 3 dtf c = 44 2 }9 6o. 

The strength of the solid plate is 

Ptf = 4I2,$00. 

___ _ . . 386,70c 

The efficiency is ■ = QS-7 per cent. 

J 412,500 yo ' ] 

Designing Riveted Joints. — One element of the design 
of a riveted joint is to secure as high an efficiency for the 
joint as is consistent with other requirements, such as a proper 
pitch for calking. 

A consideration of the example of a single-riveted lap- 
joint will show that the efficiency can be improved by increas- 
ing the diameter of the rivet and by increasing the pitch. In 
the first place, since the joint will fail by tearing between the 
rivets, simply increasing the pitch with the same size of rivet 
will give a greater efficiency. If the pitch is increased till 
the rivet fails, the failure will be by shearing. Now the 
resistance to crushing is represented by 

dtf c , 

while the resistance to shearing is represented by 



2 1 8 STEAM-BOILERS. 

that is, the resistance to crushing increases proportionally as 
the diameter, while the resistance to shearing increases as the 
square of the diameter. The shearing resistance increases the 
more rapidly, and can be made equal to the crushing resist- 
ance by using a larger rivet. Of course this will demand a 
further increase of pitch. 

In the case of the single-riveted lap-joint now under dis- 
cussion, the proper proportions for a joint that shall be equally 
strong against shearing, tearing, and crushing can be calculated 
directly. The usual way is to determine the diameter of the 
rivets by making them equally strong against shearing and 
crushing. Equating the expressions for crushing and shearing 
resistance, we have 

dtf c = f s , or a = -z — . 

Jc 4 /** 



For the case in hand with steel plates 7/16 of an inch thick, 
and steel rivets, the diameter will be 

9^000 4_Xi =M 

45,000 71 

Having the diameter of the rivets, we may now calculate 
the pitch by equating the shearing and tearing resistances, 
which gives 

d2 /s = ( P -dy /t , or p= f -;^ + J. 



4 
For the case in hand we have 



ft At 



45,000 7t l.lf 
j>= — z-+ 1.17 = 3.2. 

p 55,0004 X tV . 

The efficiency of the joint is the ratio of the resistance to 



STRENGTH OF BOILERS. 2I£ 

tearing between the rivets to the strength of a strip of plate 
having a width equal to the pitch, so that the efficiency is 

f s (p-d)t = p-d 
f s pt P ' 

In the case in hand the efficiency is 

i 3.2 — 1. 17 



00 3.2 



= 63.4 per cent. 



But the pitch calculated in this method is too great for 
proper calking with a plate of the given thickness. 

The double-riveted lap-joint has three possible ways of 
failure, which lead to two equations for finding the diameter 
and pitch of rivets. Equating the shearing and crushing 
resistance for two rivets, we have 

2—f M = 2dtf„ or d = J -^^, 
4 Js n 

which will give the same size rivet for a plate of a given 
thickness as would be found for a single-riveted joint. Now 
this method has been found to lead to too large a rivet for a 
single-riveted joint, where a strip having a width equal to the 
pitch carries one rivet. In the double-riveted joint such a 
strip carries two rivets, and consequently it is the more cer- 
tain that the method proposed will give too large a rivet, and 
of course too large a pitch for proper calking. The advan- 
tage of double riveting is that smaller rivets may be used to 
provide the requisite shearing resistance, and the plate may 
be less cut away at the section between rivets. 

In designing a double-riveted lap-joint it is customary to 
assume a diameter for the rivets and then determine the pitch 
by equating the shearing resistance of two rivets to the tear- 
ing resistance between the rivets. If the resulting pitch is too 
large for proper calking, the diameter of the rivets must be 



220 STEAM-BOILERS. 

reduced. If, on the contrary, the resulting pitch is less than 
may be allowed, a slightly larger diameter and pitch may be 
used. 

A design of a joint like the single-riveted lap-joint with 
inside cover-plate, which has a wide and a narrow pitch, 
involves some difficulty and complexity. The fundamental 
idea of such a joint is to make the resistance to tearing at the 
inner row of rivets (when the pitch is small) plus the shearing 
of the outer row of rivets greater than the resistance to tear- 
ing at the outer row of rivets (when the pitch is larger). To 
insure this condition we may proceed as follows: Equate the 
resistance to tearing at the outer row of rivets to the resist- 
ance to tearing at the inner row plus the resistance to shearing 
one rivet at the outer row. This gives 



(P - d)tf t = (P- 2d)tf t + ~/ s: 

4 
whence 

n fs' 



The result is the minimum diameter of rivets allowable. 
We may now choose a slightly larger diameter of rivets, and 
then determine the pitch in three different ways, namely, by 
equating the resistance to tearing at the outer row of rivets, 
in succession, to the resistance to shearing of three rivets, 
to the resistance to crushing in front of three rivets, and 
to the resistance to tearing between the inner rows of rivets 
and compression before one rivet. The smallest pitch 
obtained will be the correct one to use with the given diam- 
eter of rivet. Should the efficiency of the joint be unsatis- 
factory, an attempt may be made to raise the efficiency by 
increasing the diameter of the rivets. 



STRENGTH OF BOILERS. 221 

In the preceding pages it has been assumed that the strength 
of a rivet in double shear is twice that of a rivet in single shear. 
Many designers use a lower value per square inch in double 
shear than in single shear. There is but little evidence to show 
that there is any justification for this. 

The effects of crushing and shearing are so combined that it 
is difficult to get any data on double shear that is reliable. A 
careful study of all the tests made at the Watertown Arsenal, 
and of those made at the Massachusetts Institute of Tech- 
nology, failed to give any evidence that would warrant using 
a lower value per square inch for double shear than for single 
shear. 

Practical Considerations. — In proportioning a riveted 
joint, the following considerations, some of which have already 
been mentioned, must receive attention: 

The pitch of rivets near a calked edge must not be too great 
for proper calking. 

Rivets must not be too near together for convenience in 
driving. 

Punched holes must have a diameter greater than the 
thickness of the plate. 

A riveted seam must contain a whole number of rivets. 
Again, it is desirable that similar seams, as for example the 
longitudinal seams for the several rings of a cylindrical boiler, 
shall have the same pitch. 

It is evident that the design of a boiler-joint cannot be 
considered apart from the general design of the boiler. 

Flues. — The tendency of internal pressure in a thin hol- 
low cylinder is to give it a true cylindrical shape; conse- 
quently, with fair workmanship, the formulae for thin hollow 
cylinders may be applied to the calculation of boiler-shells 
subjected to internal pressure. But the tendency of external 
pressure is to exaggerate any imperfection of shape, and 
cylindrical flues fail by collapsing. 



222 STEAM-BOILERS. 

The pressure at which a flue will collapse can be found by 
direct experiment only. 

The earliest and for a long time the only tests on the 
collapsing of flues were those made by Fairbairn, and pub- 
lished in the Transactions of the Royal Society, in 1858. All 
of the tubes tested were 0.043 of an inch thick; they varied 
in diameter from 4 inches to 12 inches, and in length from 20 
inches to 60 inches. From these tests he deduced the em- 
pirical formula 



806,300 X * 2,19 
P ~ TyTd 



in which / is the length of the tube in feet and afand / are 
the diameter and thickness in inches, while/ is the collapsing 
pressure in pounds per square inch. Sometimes the exponent 
of t is made 2 instead of 2.19, for sake of simplicity. As t is 
commonly a proper fraction, the use of a smaller exponent 
will give a higher calculated collapsing pressure. 

The tubes in this series were too small, and more especially 
too thin, to serve as a proper basis for the calculation of boiler- 
flues. It is quoted because it has been widely used, and is 
now used by some engineers. It sometimes gives a calculated 
pressure higher and sometimes lower than that at which flues 
will collapse, and its use is liable to lead to disappointment if 
not to disaster. 

The following table gives the results of some tests on 
larger boiler-flues, taken from Hutton's " Steam-boiler Con- 
struction." The table gives the dimensions and the actual 
collapsing pressure, and also the collapsing pressure by Fair* 
bairn's rule and by a rule proposed by Hutton. 






STRENGTH OF BOILERS. 



223 



EXPERIMENTS ON THE COLLAPSING PRESSURE OF BOILER- 
FLUES. 



Where or by Whom Made. 



By Falrbairn 

By Fairbairn 

By Fairbairn 

By Fairbairn 

Engineering Dept., U. S. N. 

At Greenock 

By Knight 

By Knight 

By Kntght 

By J. Howden & Co., Glas- 
gow 



Dimensions. 



a) W 

5-5 

eS — 



7- 
33- 
42 
42 
54 
38 
36 
36 
36 

43 



276 

360 

420 

300 

36 

86 

24 

24 

48 

2.3 



•CO 



Collapsing Pressure in 
Pounds per Square Inch. 



■°a 

'O'u 
C V 

3 a 
o « 



no 

99 
97 
127 
128 
450 
235 
468 

390 
840 



Z2 



=2 

Ufe 



109 
81 

78 

108 

311 
740 

700 

1568 

784 

2758 



"5° 

7 

114 

"3 

100 
119 
120 
430 
218 
490 
350 

842 



On the whole the rule proposed by Hutton gives the most 
concordant results; in most cases Hutton's rule gives a cal- 
culated collapsing pressure that is smaller than the actual 
collapsing pressure; in no case is the calculated result very 
largely in excess. Fairbairn's rule in some cases shows a very 
close agreement with experiment, but in others it shows a 
dangerous excess. 

Hutton's rule is 

Ct 2 

P ~dVV 



in which I is the length in inches, d is the diameter in 



22'4 STEAM-BOILERS. 

inches, and / is the thickness in thirty-seconds of an inch. 
C is a constant which Hutton makes 600 for iron and 660 for 
steel. 

Mr. Michael Longridge, as a result of an investigation of 
many boiler -flues, most of which have endured service for 
years, but some of which failed, gives a rule in the same form 
but with a constant 540 instead of 600. 

For oval tubes and flues it is recommended that the above 
rules be applied, using for the diameter twice the maximum 
radius of curvature. 

Strengthened Flues. — It is clear from inspection of the 
preceding table of tests on boiler-flues that the collapsing 
pressure decreases as the. length of the flue increases. Account 
is taken of this in Hutton's formula, by introducing the 
square root of the length into the denominator of the expres- 
sion for calculating the collapsing pressure of a flue. Stating 
the proposition in the converse manner, the reason why a 
short flue is the stronger is that the ends of the flue are 
kept in a circular form by the plates to which the flue is 
riveted. 

It has been customary to strengthen plain flues by the aid 
of rings placed at regular intervals. The section of a ring 
made of angle-iron is shown by Fig. g&a. The ring is riveted 
to the flue at intervals, a thimble being placed over each rivet 
to give space for circulation of water between the ring and 
the flue. The rings were sometimes solid, made of one piece 
of angle-iron bent up and welded. Most frequently the ring 
was in halves, which were merely belted together at the joint. 
Such rings could be easily removed when the flue was taken 
out of the boiler. 

A better method of strengthening a flue is to make it of 
short pieces so joined at the ends as to make stiffening rings. 
Fig. 98 shows three ways in which this can be done. At b 
is shown the Adamson ring, formed by flanging the edges of 



STRENGTH OF BOILERS. 



22 i 



the short lengths of flue outwardly, and riveting through a 
welded iron ring. At c is shown a welded ring of T iron, to 
which the short lengths can be riveted without flanging. This 





Fig. 98. 

method provides for calking both inside and outside. It 
does not require the flue to be flanged; but flanging by 
machinery is rapid, and does not give trouble when good iron 
or steel is used. Material that will not stand flanging should 
not be used for flues. At d is shown the bowling hoop-ring, 
which has the advantage that it provides for longitudinal 
expansion of the flue. 

Flues for Scotch and other marine boilers with furnace- 
flues, are stiffened by transverse or helical corrugations, which 
provide at the same time for longitudinal expansion. A 
number of methods of corrugating furnace-flues will be 
illustrated in connection w T ith tests given on the following 
pages. 

Tests on Furnace-flues. — The strength of corrugated and 
other stiffened flues can be determined only by tests on full- 
sized specimens. The following tests are taken from a paper 
by Mr. B. D. Morison, read before the Northeast Coast In- 
stitution of Engineers and Shipbuilders. 



226 



STEAM-BOILERS. 



Furnaces made with Adamson Joints. 

Tests made at the Works of Hall, Russell & Co., Aberdeen, in 
1882, and of J. Howden & Co. in Glasgow, in 1887. 



■ ■ ■ *" 



Date 

of 
Test. 


Length 

of 

Furnace. 


OB 

tJC 

c 


a 

3 


ean Thickness of 
Plate. 


1) U 

rt en • 

QJaS 
3 =-* 

C l-H C 


reatest Diff. in 
Diameter at any 
Part. 


ollapsing Pres- 
sure. 


8 + 

Si i> 


ollapsing Coeffi- 
cient reduced to 
Steel of 27 Tons 
Tensile. 






£ 


2 


ta 


O 


u 


U 


U 








1st ring 












'6 ft. 5f in. total 




i" 














length. 




2d ring 












18S2 


Length of 

rings : 

i8±". 19", 19", 

and 20" 

7 ft. i in. total 


4 


15'' 

32 ' 

3d ring 

15'' 
3 2 ' 

4th ring 
1" 
2 


43 


9/64 


3d ring 
at 700 

1st ring 
at 840, 
2d ring 


64,213 


61,918 


1887 


length. 

Length of each 

ring, 23" 


4 




43-09 




at 760, 
3d ring 
at 840, 
4th ring 
at 835 


64,240 


61,945 



Note. — No record of tensile strength of steel ; 28 tons per square inch 
assumed. The collapsing coefficients are calculated on external diameter of 
furnace over plane part. 



STRENGTH OF BOILERS. 



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STRENGTH OF BOILERS. 



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STRENGTH OF BOILERS. 



231 



Purves's Patent Furnaces. 

Official Tests made at Sir John Brown & Co.'s Works at 
Sheffield in i88q. 



F^ste of Test. 



V v 



i-J rt 

05 a! 

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889. 



889 

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Dec. 23, 1890. 



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585 
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38.70 
38.72 
38.63 
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950 
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74,834 
73,034 
78,935 



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72,161 

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C6,i6o 
75,446 



Corrugations spaced 9" apart. Not very full records kept. 

Note. — The collapsing coefficients are calculated on diameters of furnaces 
over flats. 



232 



S TEA M- B OILERS. 



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STRENGTH OF BOILERS. 233 

Discussion of Results of Tests on Flues. — The stress 
in a thin hollow cylinder subjected to external fluid pressure 
may be calculated by an equation having the same form as 
that for a cylinder subjected to internal pressure; the equa- 
tion may be deduced by a similar method. Thus the stress 
will be 

s r . 

in which p is the pressure per square inch, r is the radius and 
t is the thickness, both in inches. In the table we have a 
column giving the coefficient of collapse calculated by the 
expression 

PD 
T\ 

in which Pis the pressure, D is the diameter, and J 1 is the 
thickness. The coefficient appears consequently to be twice the 
compressive stress in the flue at the time of collapsing. This 
coefficient is fairly regular for each style of furnace, and is 
somewhere near the tensile strength of the metal from which 
the flue is made; in some cases it is less and in some more 
than the tensile strength. Now soft steel in the form of short 
cylinders will begin to flow when the compressive stress in a 
testing-machine is about equal to the strength of pieces used 
for tensile tests. In other words, the tensile and compressive 
strengths are about equal. The furnaces tested appear, 
then, to have collapsed when the compressive stress was half 
the ultimate compressive strength of the metal. Now the 
limit of elasticity for both tension and compression, for soft 
steel, is about half the ultimate strength, so that the collapse 
occurred somewhere about the elastic limit. We should not, 
however, attribute too much importance to this considera- 
tion, but it will be better to follow ordinary practice and 
consider the equations used for calculating the safe working 



234 STEAM-BOILERS. 

pressure on flues to be empirical, and to depend directly on 
experiment. 

Rules for Working Pressure on Flues. — There are three 
sets of rules for working pressure on flues, which we shall 
consider; namely, those of the British Board of Trade, those 
of Lloyd 's Marine Insurance Underwriters, and those of the 
United States Inspectors of Steam-vessels. These rules are 
changed from time to time, and include certain directions to 
inspectors that need not be given here; if a boiler is built for 
inspection under these or any other rules the only safe way is 
to obtain the current edition of the rules and see that the 
boiler conforms thereto, and also that the boiler is properly 
proportioned according to the best information that can be 
obtained by the designer. 

Rules for Plain Flues. — Both Lloyd's and the United 
States Inspectors rules use for plain flues an equation in the 
form 

„ 89,600 X T* 



LD 



in which P is the working pressure in pounds per square inch, 
L is the length in feet, and T and D are the thickness and 
diameter in inches. This is Fairbairn's equation with 2 
instead of 2.19 for the exponent of T, and with a constant 



806,300 
89 ; 600 = — , 



so that the working pressure is made one ninth of the calcu- 
lated collapsing pressure by Fairbairn's rule. The use of so 
large a factor as nine shows that the rule is not considered 
adequate. Flues designed under this rule will probably be 
strong enough. 

The Board of Trade rule differs only in replacing the 



STRENGTH OF BOILERS. 235 

factor 89,600 by the approximate figure 99,000. The rules, 
however, require that the pressure shall not be greater than 

8800 X T 
P - D ' 

which provides that the stress shall not exceed 4400 pounds 
per square inch. For corrugated, ribbed, or grooved furnaces 
(such as the several furnaces for which tests are given) both 
the Board of Trade and the Inspectors rules give for the 
working pressure 

14,000 X T 
D ' 

in which P is the working pressure in pounds on the square 
inch, and Zand D are the thickness and diameter in inches. 
This rule makes the working stress 7000 pounds per square 
inch. 

Lloyd's rule for these furnaces is given by the equation 

r ~ D ' 

in which T is the thickness in sixteenths of an inch, D is the 
diameter in inches, measured over the corrugations or ribs of 
corrugated or ribbed furnaces, and over the plain part of 
Holmes' furnaces. C is an arbitrary constant having the fol- 
lowing values: 

C= 1000 for steel corrugated furnaces when the tensile 
strength of the material is under 26 tons, and corrugations are 
6 inches apart and if inches deep. 

C = 1259 for steel furnaces corrugated on Fox's or Mori- 
son's plans, tensile strength to be between 26 and 30 tons. 

C = 1 160 for ribbed furnaces with ribs 9 inches apart. 

C= 912 for spirally-corrugated furnaces. 

C = 945 for Holmes' furnaces, when corrugations are not 
over 16 inches apart and not less than two inches high. 



236 



S TEA M-B OIL ERS. 



In this rule the use of 7-2 (in sixteenths of an inch) 
instead of T is practically an allowance for wasting of the 
plate to the extent of one eighth of an inch. The working 
stress calculated on the assumed diameter will be found by 
multiplying by sixteen and dividing by two; in case of the 
first constant the stress is 



1000 X 16 
= 8000 



pounds per square inch. 

Fire-tubes. — The thickness usually given to fire-tubes to 
insure sound welding and to provide for expanding into the 
tube-sheets is in excess of that required to prevent collapsing. 
There appears, however, to be no experiments to show the 
actual collapsing pressure for such tubes. 

The joint made by expanding the tubes into the tube- 
sheets of locomotive and cylindrical tubular boilers has been 
found both by experiment and practice to be strong enough 
to secure the tube-sheet without additional staying. It is, 
however, the custom to make part of the fire-tubes of marine 
drum-boilers thick enough to take a shallow nut outside of 
the tube-plate; without such stay-tubes there is liable to be 
leakage at the ends of the tubes. 

Girders — When a flat surface cannot conveniently be 
stayed directly, it is customary to stay the surface to girders 
properly supported at the ends or elsewhere. The crown-bars 
of the locomotive-boiler shown on Plate II, and the girders 
over the combustion-chamber of the marine boiler shown by 
Fig. 11, page 17, may be taken as examples. Again, the 
channel-irons which are riveted to the flat heads of the 
cylindrical boiler shown by Plate I act as girders. 

The load which a girder of given material can safely carry 
depends on the form and dimensions of the girder, and on the 
manner of supporting and loading the girder. Some girders, 
like those over the combustion-chamber in Fig. 11, can be 



STRENGTH OF BOILERS. 237 

calculated by the simple theory of beams; others, like crown- 
bars for locomotives and the channel-bars on Plate I, can be 
properly calculated only by the theory of continuous girders. 

A proper understanding of the theories of beams and of 
continuous girders can be obtained from standard works on 
applied mechanics. An adequate statement of even the 
theory of beams is out of place in a work on boilers; an 
incomplete statement is unadvisable, since it is liable to be 
misleading. One simple example will be worked out as an 
illustration of the use of the beam theory in boiler-design. 

As an example, we will take the girders over the combus- 
tion-chamber of the marine boiler shown by Fig. 11, page 17. 
The girders are spaced 7 inches apart, and each carries three 
stays spaced 6\ incnes apart. The load on each stay-bolt at 
160 pounds steam-pressure is 

7 X 61 X 160 = 7000 pounds, 

and the total load on one girder is 21,000 pounds- The sup- 
porting force at each end of the girder is 10,500 pounds. The 
span of the girder is 22 j- inches, and the half-span is 11J 
inches. The bending-moment at the middle of the girder 
due to the supporting force acting upward, and to the load 
on one bolt acting downward, is 

10,500 X nj- - 7000 X 6J = 74,375 = M. 

Each girder is made of two plates each 5/8 of an inch thick, 
and 7 inches deep. The moment of inertia of the section of 
the girder at the middle is 

T VX2XfX7 3 = 7. 
The distance of the most strained fibre is 

7 + 2 = 3i= y- 



238 STEAM-BOILERS. 

The working fibre-stress is consequently 



f - i - T v x 2 x 1 x r - 7 * 7 



pounds per square inch. 

Stayed Flat Plates. — The method of calculating the 
stresses in a flat plate supported at regular intervals by stays 
or stay-bolts, such as the sides of a locomotive fire-box, is 
treated in the theory of elasticity, under the heading of 
" indefinite plates which are firmly held ai a system of points 
dividing them into rectangular panels." A complete solution 
of this problem is possible only when the panels are squares, 
that is, when the rows of stays are equidistant longitudinally 
and transversely., 

If the steam-pressure is represented by/, the thickness of 
the plate by t, and the pitch of the stays by #, then the 
direct working stress, which is a tension at certain places and 
a compression at others, is given by the formula 

The maximum deflection is given by the equation 

I pa' 
36 Ef ' 

in which E is the modulus of elasticity of the material. 

If the sheets of a locomotive fire-box, or other stayed 
plates, have a direct tension or compression, proper allowance 
must be made for it. 

If stays or stay-bolts are in rows that are not equidistant 
each way, as for example the through-stays in the steam- 
space in Fig. 11, page 17, then the largest pitch may be used 
in the above equations. The actual stress will in such case be 
less than the calculated stress by an unknown amount. If, 



STRENGTH OF BOILERS. 239 

further, stays are arranged irregularly, the greatest distance 
in any direction may be used in the equations, but the calcu- 
lated stress may then be very different from the actual stress; 
it is, however, always the larger. 

As an example, we may calculate the stress in a side sheet 
of the locomotive fire-box shown on Plate II. Here the 
rows of rivets are four inches apart each way, the plate is 
5/16 of an inch thick, and the steam-pressure is 170 pounds. 
The maximum stress is 

Now the crown-bars are bedded on and are partly sup- 
ported by the side sheets of the fire-box. The crown-sheet 
is 72 inches long and 45! inches wide, and has an area of 

72 X 45l - 3285 
square inches, and is subjected to a pressure of 

3285 x 170 = 55M50 

pounds. The distribution of this load between the side 
sheets and the sling-stays can be determined only by the cal- 
culation of the crown-bars as continuous girders, and may be 
disturbed by the expansion of the fire-box and by other 
causes. If it be assumed that the side sheets carry half the 
load on the crown-bars, then one side sheet will carry one 
fourth of 558,050, or 139,512 pounds. The side sheet is "]2 
inches long and 5/16 of an inch thick, so that the stress per 
square inch from the load on the crown-bars is 

139,512 -^ 72 X A = 62 °° 

pounds, — about as much as the stress calculated above. The 



2 40 S TEA M-BOILERS. 

total compression on the side sheet is therefore about 12,400 
pounds per square inch. 

This calculation, which appears sufficiently simple, illus- 
trates the danger of making calculations by formulae without 
knowing how they are derived and how they should be 
applied. The formula for staying given above is often 
quoted without any reference to tensile or compressive stress 
on the stayed sheet, from other causes; the use of such a 
formula by one who is unfamiliar with the theory of elasticity 
may lead to serious error in design. 

Factor of Safety. — The reciprocal of the ratio of the 
working pressure of a boiler to the pressure at which the 
boiler or any part of a boiler may be expected to fail quickly, 
is called the factor of safety for the boiler or for that part of 
the boiler. 

It is commonly recommended by writers that a factor of 
safety of six shall be used for boilers; probably such a factor 
would be economical for a boiler that is expected to work 
continuously for many years, as it allows a margin for deteri- 
oration. If the stresses coming on the parts of a boiler can 
be determined, a general factor of five will give sufficient 
security. If the boiler is carefully watched, a factor of four 
may be used; many boilers are worked with this factor. The 
use of an excessively large factor of safety, for example of the 
factor nine for flues calculated by Fairbairn's equation, shows 
a lack of confidence in the method. It is proper to make 
allowance for corrosion of parts like stays: this may be done 
either by using a larger factor of safety, or by a direct allow- 
ance; thus all stays, whatever their diameters, may have an 
eighth of an inch added to the diameter to allow for corrosion. 
It is of course proper in any structure to make small but im- 
portant members, such as stays in boilers, large enough to 
place them beyond any suspicion of failure. 

Hydraulic Tests of Boilers. — It is customary to subject 
new boilers to a water-piessure considerably in excess of the 
working pressure, to discover any leaks at riveted joints, at 



STRENGTH OF BOILERS. 24 1 

the tube-sheets, or elsewhere; should there be any gross 
defect of design or workmanship it will be developed by this 
hydraulic test. Old boilers after repairs are subjected to a 
hydraulic test for the same purpose, but the pressure is not 
carried so high as for new boilers. 

The pressure applied during a hydraulic test is seldom 
more than once and a half the working pressure, and as most 
boilers have an actual factor of safety of not more than five, 
and frequently of four, it is apparent that the recommenda- 
tion of some authors, that the test pressure should be twice 
the working pressure, cannot ordinarily be followed without 
danger of injuring the boiler. With a factor of safety of six 
there should be no danger of injuring the boiler by applying 
a hydraulic pressure equal to twice the working pressure. 

It should be borne in mind that some of the worst stresses 
that come on the different parts of the boilers are due to 
unequal expansion and contraction, and that such stresses are 
not set up during a hydraulic test. Finally, the fact that a 
boiler has successfully withstood a hydraulic test is not a con- 
clusive proof that it is safe; too many unfortunate explosions 
of boilers, more frequently old boilers, after a hydraulic test, 
have shown this. 

The safety of a boiler is to be insured by careful and cor- 
rect design, honest and thorough workmanship, and intelli- 
gent care in service. Forms and methods of design and 
construction that do not admit of ready calculation should be 
avoided; in no case should the ordinary hydraulic test be 
relied upon to guarantee the strength of parts that cannot be 
calculated with a fair degree of certainty. If such forms are 
used in any case, they ought to be tested separately to a 
pressure of two or three times the working pressure, and some 
examples of each form and size ought to be tested to destruc- 
tion. 

The boiler undergoing a hydraulic test snould be carefully 
inspected, and any notable change of shape or leakage should 



242 S TEA M-B OILERS. 

be investigated to discover the cause. Frequently small leaks 
that are developed during a test are stopped at once by 
calking or otherwise, but it is preferable to mark the place 
of the leak and calk after the pressure is removed. This of 
course requires another test to find out if the calking is suc- 
cessful. 

The pressure is usually applied by filling the boiler entirely 
full of water and then pumping in enough water, by hand or 
by power, to supply the leaks and develop the pressure 
required. If the pumping is done by hand, it is desirable to 
carefully remove all air from the boiler to avoid the labor of 
compressing air up to the test pressure. If the pumping is 
done by power, the saving of work is of less consequence, and 
a little air remaining in the boiler will act as a cushion, and 
lessen the shocks due to the strokes cf the pump. 

New boilers are tested on the boiler-shop floor; old boilers 
are commonly tested in their settings, and in such case the 
inspection during a test is less convenient and efficient. 

It is sometimes recommended that hot water shall be used 
for testing a boiler; but there seems to be no advantage in 
so doing, as it is unequal expansion, and not merely rise of 
temperature, that sets up the unknown stresses that are so 
destructive to the boiler. Of course the use of hot water 
makes an efficient inspection during the test difficult if not 
impossible. 

When there is no other way of applying the hydraulic test 
to a boiler in its setting, the boiler may be quite filled with 
water, and then a light fire may be started in the furnace. 
The expansion of the water will develop the required pressure 
at a much less temperature than that of steam at the same 
pressure, and with less danger should the boiler fail. This 
method cannot be recommended for general use; and in case 
it is followed care must be taken not to exceed the desired 
pressure. 



STRENGTH OF BOILERS. 243 

Hydraulic Test to Destruction. — In 1888 a boiler-shell, 
made to represent a part of the shell of a gunboat boiler, was 
tested by hydraulic pressure at the Greenock Foundry,* with 
the intention of bursting it. The shellwas 11 feet long and 
7 feet 8 T 3 F inches mean diameter. It was made of three sec- 
tions of 19/32 plate, triple-riveted, with butt-joints and double 
cover-plates at the longitudinal joints, and lapped and double 
riveted at the ring seams. The rivets were staggered for both 
longitudinal and ring seams. The end-plates were 20/32 
thick, and stayed with through-stays and washers, spaced 14 
inches on centres. The stays were ij inches in diameter; 
the screws at the ends of the stays were 2 \ inches in diameter. 
Finally, it may be said that the shell was designed to fulfil 
the Admiralty specifications for a working pressure of 145 
pounds per square inch. The workmanship was of the same 
degree of excellence usual for boiler-work at that establish- 
ment. 

First Test. — The shell was first subjected to the working 
pressure of 145 pounds, and showed a slight alteration of form 
due to the tendency of internal pressure to give it a true cylin- 
drical form. The pressure was then raised to the Admiralty 
test pressure of 235 pounds, and then to 300 pounds without 
developing leaks. There were some minor changes of form 
due to the increase of pressure. The pressure was then 
removed and the shell returned to its original dimensions. 

Pressure was then raised to 330 pounds, when there was a 
slight leak at the manhole door. At 450 pounds pressure 
the leak at the manhole door exceeded the capacity of the 
pumps. There was also a slight leak at the corners of two 
butts. The manhole was then strengthened — no other repairs 
were made. 

Second Test. — Pressure was raised to 350 pounds and 
developed a small leak at the manhole. There were slight 

* Trans. Inst. Naval Arch., vol. xxx. p. 285. 



2 44 S TEA M-BOIL ERS. 

leaks at the butt-straps, which were calked at the end of the 
test. The manhole, however, leaked so that the test was 
stopped. 

TJiird Test. — After additional bolts were put into the 
manhole cover the pressure was raised to 350 pounds with- 
out leakage. At 360 pounds the manhole began to leak, and 
at 580 pounds the test was stopped on that account. The 
butt-straps opened visibly at the calking and leaked more 
than before. 

Fourth Test. — The butt-joints were again calked and 
additional pumps were employed. The shell was again tight 
at 350 pounds and the pressure was carried to 620 pounds, at 
which there was a good deal of leakage at the butt-straps. 
Only one or two rivets showed signs of leakage; there 
appeared to be no difference between the hand and machine 
riveting in this respect. At the pressure of 620 pounds the 
entire capacity of the pumps was required to supply the 
leakage. 

The distortion of the shell was very marked at the higher 
pressures, and increased with the pressure; thus the ends 
bulged an inch at 520 pounds, about \\ inches at 580 pounds, 
and nearly two inches at 620 pounds. The sides bulged more 
irregularly, but to the extent of nearly an inch at 620 pounds. 
The stays drew down uniformly 1/64 of an inch at 520 
pounds, 2/64 at 580 pounds, and 4/64 at 620 pounds. They 
increased in length 2^ inches at 520 pounds, 3^ inches at 
580 pounds, and 3f inches at 620 pounds; this accounts for 
the bulging of the end-plates. 

The mean tensional strength of the plates from which the 
shell and butt-straps were made may be taken at 61,500' 
pounds. At 620 pounds the tension on the plates between 
the rivet-holes was 57,504 pounds, or 93^ per cent of the 
strength of the solid plate, and there was no serious disturb- 
ance of the structure. The ring seams increased in diameter 
about f of an inch, and the shell bulged out between them. 



STRENGTH OF BOILERS. 245 

The various portions of the boiler acted in harmony and 
showed no special weakness at any point. The butt-joints 
had the rivets spaced 5f inches on centres to give a percen- 
tage of 83.7 per cent of the plate, and this may have caused 
the leakage found there. The riveting appeared to be 
reliable at the extreme pressure reached. This test seems to 
show that a boiler will give signs of weakness long before it 
will fail. Such signs of weakness should be carefully investi- 
gated : if there is any local weakness or deterioration, repairs 
or alterations may be made; if there are evidences of general 
deterioration, the working pressure must be reduced, or 
better, the boiler may be replaced by a new one. 

Boiler-explosions. — The great destruction of life and 
property that is liable to be caused by a violent boiler-explo- 
sion makes it imperative that the causes should be carefully 
investigated, to the end that explosions may be prevented. 

With this in view the boiler and its parts, and any wreck 
or evidence of destruction caused by the explosion should be 
left undisturbed until the scene of the explosion can be 
examined by a competent engineer. Of course if any persons 
are injured by the explosion they must be rescued and cared 
for immediately, and also any building or structure that is so 
injured as to threaten life or safety must be attended to at 
once; but it should be borne in mind that the examination by 
the engineer for the purpose of determining the cause of the 
explosion is also in the interest of humanity, since its aim is 
to avoid future explosions. All idle or simply curious per- 
sons should be excluded from the scene of the explosion, more 
especially as such persons are apt to disturb or even carry 
away things that may be of importance in the study of the 
cause and history of the explosion. If the explosion is 
accompanied by loss of life or injury to person or property, 
it will be followed by a leg;al investigation in which the testi- 
mony of the engineer or engineers who have examined the 
scene of the explosion will be of prime importance, as it will 



246 S TEA M- BOIL ERS. 

have a large influence in locating responsibility for the 
disaster. 

While various causes may lead to boiler-explosion, it is 
unfortunately true that by far the greater part of violent 
explosions are due to the fact that the boiler is too weak to 
endure service at the regular working pressure. A new boiler 
may be weak through defective design or workmanship; 
there can be no excuse for the explosion of a new boiler from 
weakness, and such explosions in good practice are rare. An 
old boiler is liable to become weak through local or general 
corrosion or other deterioration; this amounts to saying that 
a boiler will eventually wear out. 

The length of time that a boiler will endure service 
depends (1) on the design, (2) on the thickness of plates and 
the quality of the metal, (3) on the workmanship, (4) on the 
care given it, and (5) on the quality of the feed-water. 
Definite figures cannot be given for the life of a boiler, since 
it depends on so many things. The following table gives the 
number of years several kinds of boilers can endure regular 
service if they are properly built and cared for: 

Lancashire, low-pressure 1 5 to 20 years. 

Locomotive type, stationary 12 to 1 5 

Locomotive-boilers 8 to 12 

Vertical boilers 10 to 15 

Vertical boiler with submerged tubes... . 14 to 18 

Horizontal cylindrical tubular .... 15 to 20 

Scotch marine boiler 1 2 to 1 5 

'Water-tube boiler 12 to 16 

Pipe or coil boiler , 5 to 8 

By water-tube boiler is here meant a boiler with a shell 
or drum containing a considerable body of water. By pipe 
or coil boiler is meant a boiler made up of pipe and pipe- 
fittings, with a separator. 



STRENGTH OF BOILERS. 



247 



Horizontal boilers will require one, and vertical boilers two 
extra sets of tubes, before the shell is condemned. A loco- 
motive-boiler will require two extra sets of tubes, and the 
entire fire-box will be renewed once in the life of the boiler. 

If boilers are subjected to careless or ignorant abuse, they 
may be used up in a fraction of their proper time of service, 
especially if cheaply built. This will account for the numer- 
ous explosions of sawmill boilers and agricultural boilers. 

It has been pointed out that leakage is frequently a sign 
of weakness; a perversion of this idea leads to the assumption 
that a boiler is safe as long as it can be kept from leaking. 
Too many boiler-explosions have this history: The boiler, 
after long and satisfactory service, began to leak; a cheap 
man was employed to repair the boiler, the repairs consisting 
mainly of excessive calking to stop the leaks; soon after the 
repairs, perhaps the first time the boiler was fired up, it 
exploded violently. A fit conclusion of the history is to 
ascribe the explosion to some obscure cause or to carelessness 
of the attendant, if he was killed by the explosion. 

Serious injury may be caused by overheating any part of 
the heating-surface, due to low water, to defective circulation, 
or to deposits of non-conducting substance on the plates or 
tubes. The overheated member, or plates, of the boiler may 
burst or collapse, and such failure may lead to an explosion 
of the boiler, but frequently the escape of steam and water 
will check the fire and relieve the pressure on the boiler. 
Local failures are dangerous to the boiler attendants, especially 
in a confined fire-room, as on shipboard. Unless there is 
direct evidence of overheating, either from known circum- 
stances before the explosion or from signs on the boiler after 
explosion, the cause of the failure should be sought elsewhere. 

If a boiler shows signs of low water or of overheating the 
fire should be checked by any effectual means. The most 
ready way of checking the fire is to close the ash-pit doors and 
throw ashes onto the fire. If there are no ashes at hand, then 



248 STEAM-BOILERS. 

fresh fuel may be used instead, since its first effect is to deaden 
the fire. There will be time for caring for, or drawing the fire 
before the fresh fuel is fairly in combustion. An attempt to 
draw the fire without first deadening it is liable to give a fierce 
combustion for a short time; moreover, more time is required 
to draw the fire. If the furnace has a dumping-grate, the fire 
may be immediately thrown into the ash-pit without waiting 
to deaden it. The damper should be left open so that if a 
rupture occurs the steam may escape up *-he chimney. Mean- 
while the steam made by the boiler should be disposed of by 
allowing the engine to run or by any other means, for exam- 
ple by opening the safety-valve, provided that it is merely a 
case of overheating, not accompanied by excessive pressure. 
It will probably be well to start the feed-pumps or to increase 
the supply of feed-water. Should the introduction of feed- 
water be badly arranged so that a large volume of cold water 
will be thrown onto a heated plate, it is possible that starting 
the feed-pump may cause a contraction which will start a 
rupture. 

It has been found by experiment that boiler-flues that 
have been purposely allowed to become bare and overheated 
have been saved by suddenly directing a stream of cold feed- 
water upon them, though such treatment may make them 
leak at the joints. The heat stored in such hot plates is 
insignificant as compared with the heat in the water and steam 
in the boiler. 

Excessive pressure, especially if it is enough to give good 
reason to fear an explosion, is more difficult to deal with; the 
chances of success are less and the risks are greater than when 
the water is low, but the pressure is not excessive. If possi- 
ble the fire should be checked and the pressure relieved. The 
first may be done by throwing on ashes or cold fuel, and the 
second by running the engine at full load. It is at least 
doubtful whether starting the feed-pump will reduce the 
pressure fast enough to do much good, and on the other hand 






STRENGTH OF BOILERS. 249 

there may be cases where such action would start an explo- 
sion. It is not best to open the safety-valve, since the sudden 
opening of a large safety-valve gives a shock which may 
determine the explosion. Some explosions have been re- 
ported that occurred immediately after the safety-valve 
opened. 

A large amount of energy is stored in the steam and water 
in a boiler in the form of heat. An idea of the amount of 
energy in any given case may be obtained by a simple calcu- 
lation. Thus the cylindrical boiler shown on Plate I, at 150 
pounds pressure by the gauge, will contain 6600 pounds of 
water and 22 pounds of steam. 

The total weight of water and steam is 6622. The fractional 

22 
weight which in steam is 77— =.003 32. Should the boiler ex- 
fe 6622 °° 

plode the mixture of water and steam would expand adiabati- 
cally to atmospheric pressure. A portion of the water would 
have vaporized. The percentage of the entire weight which is 
steam after the explosion has taken place may be found by equat- 
ing the entropy at the two points. 

Calling xi the fractional weight which is steam at the start 
and X2 the fractional weight at 212 ; r x and r 2 the heats of vapori- 
zation at boiler pressure and at 212 respectively, T\ and T2 
the absolute temperatures, and 0\ and d 2 the entropies of the 

X\fi OC2T2 

liquid we have that -7=— + 0!=-= — \-d 2 . If we call the boiler 
1 \ 1 2 

pressure 165 pounds absolute 

.00332 X85 5 . 9+ ^2X966.3 

365.9 + 459.5 * 5 35 459.5 + 212 * 3125 ' 

#2 = .15, or about 15 per cent is steam. 

The work done comes from loss of intrinsic energy and is in 
this case equal to 

6622 X 778(?i +xipi -q 2 -X2p2), 



250 STEAM-BOILERS. 

where qi and q 2 are the heats of the liquid at the two pressures 
and pi and p 2 are the internal latent heats. Substituting values 
for these, the expression reduces to 6622 X 778(337. 7 + .00332 X 
772.2- 180.3 -.15X893.9) = 132,331,000 foot-pounds. 

If the entire explosion took place in two seconds, work was 
..developed at the rate of 120,300 horse-power. 

If a calculation is made for this same boiler, assuming that the 
boiler was "dry," or just filled with steam, the energy developed 
would be between 5 and 6 million foot-pounds instead of 130 
million. 

A person can sometimes judge as to whether the boiler was 
dry or not at the time of the explosion by the amount of destruc- 
tion caused by the explosion. 

The more water a boiler contains the greater the damage done 
Jby an explosion. 

An explosion of a boiler carrying low pressure for heating will, 
:if there is a considerable amount of water in the boiler, develop a 
number of millions of foot-pounds of energy. 

Lap-seam Boilers. — It has already been mentioned that 
pressure on the inside of a cylinder tends to bend out any flat 
places and to make the shell a true circle, while pressure on the 
outside of a cylinder tends to make the cylinder collapse. Any 
flat places in such a cylinder will make the cylinder collapse at a 
much less pressure. This has been shown by experiments on 
upright boilers. The fire-box always begins to collapse at the 
seams where one part of the circle laps over the other part because 
at this spot there is a flattened area. If in the staying of the 
Tvater-leg of a vertical boiler an extra line of screwed stay-rivets 
be put through this joint the collapsing pressure will be raised 
from 15 to 20 per cent. 

The longitudinal joint on a horizontal multitubular boiler 
comes from 2 to 6 inches above the top of the brackets support- 
ing the boiler. There is considerable stress thrown into the joint 
t>y the load on the brackets. The tendency of the pressure inside 
of the boiler and the tension in the shell is to pull the flattened 



STRENGTH OF BOILERS. 251 

area at the joint into a true circle. The bending takes place at 
the rivet holes. The force tending to pull the joint into a circle 
varies every time the boiler pressure changes. These repeated 
bendings may after a long period start a crack which gradually 
gets deeper and finally determnies the life of the boiler. 

Sometimes an internal inspection of the boiler may show such 
cracks, but more often the crack starts between the two plates 
where one laps over the other. A crack in this place could not 
be found either by an internal inspection or by an external inspec- 
tion. A cold-water test might show this defect if the water 
pressure was made great enough. 

A number of boiler explosions have resulted from cracks of 
this sort. 

A lap-seam boiler may wear out before this repeated bending 
action at the joint starts a crack. If the plate used was ductile 
and the workmanship was good such probably would be the case. 



CHAPTER IX. 
BOILER ACCESSORIES. 

In this chapter will be described various fittings, attach- 
ments, and accessories for steam-boilers. 

Valves are used to control and regulate the flow of fluids 
in pipes. They are variously named after their forms or uses, 
such as globe valves, angle-valves, straightway valves, and 
check-valves. 



C 



I A- 



} 




Fig. 99. 

Globe Valves are named from the globular form of their 

cases. The case is separated into two parts by a diaphragm 

with a passage through its horizontal part, as shown in Fig. 

99. The fluid enters at the right, passes under the valve, and 

252 






BOILER ACCESSORIES. 



'53 



out at the left. The valve is shut by screwing down the 
handle on the valve-spindle. A stuffing-box around the 
valve-spindle prevents leakage of fluid. In this valve the seat 



S^K 



J J =R 




5 PIPE TAP 



Fig. ioo. 



is rounded, and the valve face is a ring of a peculiar composi- 
tion, let into the valve at R. When the valve is shut, this 
composition is squeezed down onto the seat and makes a 
tight joint. 

If the fluid enters the valve from the right-hand side, the 



254 



STEAM-BOILERS. 



valve-spindle may readily be packed to prevent leakage while 
the valve is closed. If the fluid entered the valve at the 
other end, it would be necessary to shut ofT the fluid from 
the entire pipe in order to pack the valve. 

Angle-valves. — This form of valve, shown by Fig. 100, 
has an inlet at the bottom and an outlet at one side, it may 
take the place of an elbow at a bend in piping. The valve 
is made in two parts. The upper part carries a ring of soft 
metal which forms the bearing-surface. The lower part has 
ribs or wings which enter the opening through the valve-seat 
and guide the valve to its seat> The valve-spindle has a 




Fig. ici. 



sorew at the upper end which passes through a yoke entirely 
outside of the body of the valve. 

The body of the valve is made of cast iron. The valve, 



BOILER ACCESSORIES. 



255 



valve-seat, valve-spindle, and stuffing-box follower are made 
of brass or composition. 

This form of valve is frequently used for the stop- valve 
between the boiler and the main steam-pipe. 

Straightway or Gate Valve.— This form of valve gives 
a straight passage through the valve, and offers very little 
resistance to the flow of fluids when it is open. Fig. 101 
represents a Chapman valve, in which the valve is wedge- 





Fig. 102. 



shaped and is forced against a wedge-shaped seat. The valve- 
spindle is held at a fixed height by a collar, and draws up or 
forces down the valve to open or close it. The body of the 
valve is of cast iron ; the valve, valve-spindle, and stuffing-box 
are ot brass-, the valve-seat is a soft composition. 

Fig. 102 represents a Peet valve, which has the faces of the 
valve -seats parallel. The valve itself is made in two pieces, 



256 



STEAM-BOILERS. 



between which is a peculiar casting, U shaped at the bottom 
and with wedge-shaped lips at the top. When the valve is 
shut this casting rests on the bottom of the valve body, and 
the two halves of the valve are thrown against the parallel 
valve-seats by the wedge-shaped lips of the casting. When 
the valve is opened this casting hangs between the two halves 
of the valve by the under side of the wedge-shaped lips 

Check-valves allow fluids to pass in one direction, but 
not in the other. Fig. 103 represents a lift check- valve; it 





Fig. 103. 



Fig. 104. 



resembles a globe valve without a valve-spindle. Fluid 
entering at the left will lift the valve and pass out at the 
right. Should the current be reversed the valve will be 
promptly closed. 

Fig. 104 represents a swing check-valve. It offers less 
resistance to the flow of fluid than the valve shown above, 
and there is less chance that foreign matter will lodge on the 
valve-seat. The valve has some looseness where it is fastened 
to the swinging arm, so that it may properly seat itself. 

A feed-pipe must always have a check-valve to keep the 
boiler-pressure from acting on tne pump, or injector, when it 
is not at work. It automatically opens to allow water to pass 
into the boiler. There should also be a stop-valve (a globe or 
gate valve) near the boiler which can be shut at will; thus 
when the check-valve shows signs of leaking the stop-valve 



BOILER ACCESSORIES. 257 

may be shut, and then the check-valve may be opened and 
examined. 

Safety-valves are intended to prevent the pressure oi 
steam from rising to a dangerous point. In order to accom- 
plish this, the effective opening of the valve should be suffi- 
cient to discharge all the steam that the boiler can make 
when urged to its full capacity. The effective opening is 
equal to the circumference of the valve-seat multiplied by the 
lift of the valve, ii the valve-seat is flat; if the valve-seat is 
conical, the lift should be measured at right angles to the 
seat. Then if / Is the vertical lift and if a is the angle which 
the seat makes with the vertical, the effective lift is 

/ sin a, 

The lift of a safety-valve rarely exceeds 1/10 of an inch. 
A two-inch pop safety-valve, made by the Crosby Gauge and 
Valve Co., and tested at the laboratory of the Massachusetts 
Institute of Technology, was found to lift from 0.07 to 0.08 
of an inch. The valve had a conical seat with an angle of 
45 . The actual flow was about 95 per cent of the calculated 
flow for this valve. 

The amount of steam that a boiler can make may be 
estimated from the grate-area, the rate of combustion, and the 
evaporation per pound ot coal. The first item is fixed, and 
the other two, though somewhat indefinite, may be estimated 
from the type of boiler and the conditions under which it 
works. 

For example, a factory boiler having a grate 5 feet by 6 
feet may be assumed to burn 18 pounds of coal per square 
foot of grate-surface per hour, and to evaporate 8 pounds of 
water per pound of coal. It will therefore generate 

5X6X18X8 At* 

7 -z. = 1.2 pounds of steam per second. 

60 X 60 r i 

The amount of steam which will be delivered by a safety^ 



258 STEAM BOILERS. 

valve may be calculated by an empirical equation proposed 
by Rankine; it may be written 

in which W is the weight of steam in pounds delivered per 
second, A is the effective area of discharge in square inches, 
and p is the absolute pressure of the steam in pounds per 
square inch. 

If the weight of steam to be discharged per second is 
known, then this equation may be used to calculate the 
effective area; and will then read 

_ 70 W 

In the example given above the weight of steam per second 
is 1.2 pounds. If the steam-pressure is 100 pounds absolute 
(85.3 by the gauge), then the effective area must be 

70 X 1.2 

A = / —^ =0.84 

100 ^ 

of a square inch. If the effective lift be assumed to be 0.075 
of an inch, the circumference of the valve-seat should be 

0.84 -f- 0.075 = ri - 2 inches, 

and the diameter should be 3.5 inches. 

A common rule requires that there shall be an area of 1/3 
of a square inch through the valve-seat foi each square foot 
of grate-surface. It so happens that this rule gives almost 
identically the same result as that just calculated for the above 
example; thus: 

5 X 6 



10 square inches, 



V 



— — 3.5 -\- inches, diameter. 



BOILER ACCESSORIES. 



2 59 



This rule will apply only to a certain rate of coal consump- 
tion: 15 to 20 pounds per hour per square foot of grate or 130 
to 160 pounds of steam made per hour from a square foot of 
grate. 

The method, given on the preceding page, wherein the actual 
amount of steam made is considered, is the only correct method 
of calculating the size of a safety-valve. 

Lever Safety-valve. — The general arrangement and some 
of the details of a well-made safety-valve are show/i by Fig. 
105. 



I 



WEIGHT 
115 LBS. 



CENTER OF GRAVITY 
OF LEVER 

WEIGHT OF LEVER 42 LBS 

WEIGHT OF VALVE AND 

SPINDLE 15 LBS. 




Fig. 105. 



The body of the valve is of cast iron, and has an opening 
at one side from which the escaping steam is led out of 
the boiler-room through an escape-pipe. The valve and 
valve-seat are of brass or composition; the bearing-surface is 
at an angle of 45 with the vertical. The load is applied by 
a steel spindle, to a point beneath the bearing-surface so that 
the valve is drawn down to its seat. The spindle passes 
through a brass ring in the cover to the valve-casing. The 
load is applied by a lever with a fulcrum at A and a weight 
at D. It is steadied by guides cast on the cover of the 
casing; in the figure the valve and body are shown in section, 
but the spindle, lever, guides and weight are shown in eleva- 
tion. 

It is important that the pins ar A and B shall be loose in 
their bearings, and that the spindle shall be free where it 



260 STEAM-BOILERS. 

passes through the top of the valve-case, so that the valve may 
not fail to rise even if the working parts are rusted a little. 

After a safety-valve has blown off it is liable to leak a 
little, and such leakage is likely to injure the bearing-surface. 
In this way safety-valves sometimes get leaky and trouble- 
some. The proper way is to regrind the valve and make it 
tight, but if the boiler attendant is careless he may try to 
stop the leak by jamming the valve on its seat. This may 
be done by hanging on extra weight, or wedging a piece of 
wood or metal against the lever. To remove temptation, it 
is well to have the guides for the lever open at the top, and 
also to cut off the lever to just the proper length so that the 
weight cannot be slid farther out. A short lever and a heavy 
weight are better, for this reason, than a lighter weight and a 
longer lever. 

In order to make a calculation of the pressure at which a 
safety-valve will blow off, we must know the diameter of the 
valve, the weight of the valve and valve-spindle, the length 
of the lever and the weight hung at its end, and the weight 
and centre of gravity of the lever. This last may be found 
by calculation, or more simply by balancing the lever on a 
knife-edge. 

In the example shown by Fig. 105 the valve has a diameter 
of 5 inches and an area of 

3.1416 X 5 3 <• 

±-^— = 19.635 

4 

square inches, on which the steam presses. 

The valve and spindle weigh 15 pounds; this is applied 
directly at the valve. The weight of 115 pounds at the end 
of the lever, is 56 inches from the fulcrum at A. It is equiva- 
lent to a weight of 

1I52L56 = l6 io 






BOILER ACCESSORIES. 261 

pounds at the valve. The weight of the lever is 42 pounds, 
applied at the centre of gravity C, 20 inches from the fulcrum. 
It is equivalent to a weight at the valve of 

42 X 20 
= 210 



pounds. The total equivalent weight, or the load on the 
valve, is 

15 + 1610 -f- 210 = 1835 pounds. 

Since the area of the valve is 19.635 square inches, the 
steam-pressure per square inch required to lift the valve will 
be 

1835 -f- 19.635 = 93.46 pounds. 

Problems concerning the loading of a safety-valve may be 
conveniently stated and solved by taking moments about the 
fulcrum ; that is, by multiplying each weight or force by its 
distance from the fulcrum. 

Let the weights of the valve, spindle, lever, and weight 
be represented by V, S, L, and IV. Let a be the distance of 
the weight from the fulcrum and b be the distance from the 
fulcrum to the valve, while c is the distance of the centre of 
gravity of the lever from the fulcrum. 

The moment of the weight is Wa, and the moment of the 
lever is Lc. The moment of the valve and spindle is (V -\-S)&. 
All three moments act downward, and their total effect is equal 
to their sum, 

Wa + Lc + (V+S)b. 

If the diameter of the valve is d, then the area is ^nd 2 . 
Representing the steam-pressure above the atmosphere by/, 
the force acting on the valve is 

Ttd" 



262 STEAM-BOILERS. 

and the moment of that force is 

■ — pb. 

This moment acts upward and, when the valve lifts, will 
be equal to the total downward moment. So that the equa- 
tion for calculating the load on a lever safety-valve is 

/£— = Wa + Lc+ (V+ S)b. 

This equation gives for the steam-pressure at which the 
valve shown by Fig. 89 will lift 

4 [Wa+Le+(V-S)b] 

P ~ 7td*b 

4(115 X 56 + 42 X 20+ 15 X4) 
' ' P 3-I4I6 X 5 2 X 4 

. •. p = 93.46 pounds, 

as found by the previous calculation. 

For a second example let us find the distance at which 
the weight of the valve shown by Fig. 105 must be placed 
from the fulcrum in order that the valve will blow off at 50 
pounds above the atmosphere. 

Solving the general equation for a, we have 

nd* 
pb Lc- (V+S)b 



So X 4 X 3 '\ 41 X 5 2 - 42 X 20 - 15 X 4 
.. a= ^ ( 

„\ a = 26.32 inches. 



BOILER ACCESSORIES. 263 

For a third example find the weight which should be hung 
at the end of the lever if the valve is to blow off at 30 pounds 
above the atmosphere. 

Here we have 



nd* 

pb — Lc-(V-\-S)b 



W = 



W = 



30 X 4 X *— — X5 -42X20-15x4 



56 



W — 26 pounds. 



These last two problems can of course be stated and 
solved much after the first manner applied to the first problem, 
but the work, which will amount in the end to the same 
thing, cannot be so well arranged nor so easily done. 

Pop Safety-valve. — A defect of the common lever 
safety-valve is that it does not close promptly when the 
steam-pressure is reduced, and it is apt to leak after it has 
returned to its seat. 

The valve shown by Fig. 106 has a groove turned in the 
flange which projects beyond the bearing-surface, and there is 
another groove between the outer edge of the valve-seat and a 
ring which is screwed onto the valve-seat. When the valve 
lifts the escaping steam is twice deflected, once by the groove 
in the valve and again by the groove at the valve-seat. The 
reaction of the steam assists the pressure of the steam on the 
under surface of the valve, and suddenly opens the valve to 
its full extent. The valve stays wide open till the steam- 
pressure in the boiler has fallen a few pounds below the blow- 
ing-off pressure, and then the valve shuts as suddenly as it 
opens. 

The ring which is screwed onto the valve-seat has a number 



264 



STEAM-BOILERS. 



of holes drilled through it to allow steam to escape from the 
groove at its upper surface. It may also be screwed up or 




Fig. 106. 

down to adjust its position; a screw at the side of the case 
clamps it when adjusted. The action of the valve is regulated 



BOILER ACCESSORIES. 265 

by the number of holes in the ring and by its vertical posi- 
tion. 

This valve is loaded by a helical spring. The tension of 
the spring and the load on the valve is regulated by a sleeve 
which is screwed down through the top of the valve-case. It 
is of course possible to load a plain safety-valve in a similar 
way, or to load a pop-valve with a lever and weight. The 
valve is extended up in the form of a thin shell to guard the 
spring from the escaping steam. The valve-spindle is ex- 
tended through the top of the case, and may be pulled up 
by a lever when it is desired to ease the valve off from its 
seat. A drip at the lower right-hand side of the case draws 
off water which may collect in the case. 

The valve and its seat, the adjusting-ring on the seat, the 
valve-spindle, and the bearing-pieces on the spring are all 
brass. There is also a brass ring inside the shell that extends 
down from tlie cover and incloses the spring. There should 
be a little clearance between this brass ring and the shell on 
the valve so that the valve shall not be cramped. The entire 
valve-casing, which is made in four parts, is of cast iron. 

It is evident that the annular space between the bearing- 
surface and the edge of the groove of the valve in Fig. 106 is 
subjected to a pressure, when the valve is open, which 
depends on the rates of flow to and from this space. Some 
pop-valves depend mainly, if not wholly, on such an additional 
pressure for their action, and it is claimed by some makers 
that all pop-valves do. The closeness of regulation by a pop- 
valve may be controlled by determining the width of the an- 
nular space and by adjusting the grooved ring outside the 
valve-seat. Valves have been made with only two pounds 
for the range of pressure between opening and closing; thus, 
a pop-valve may open at 100 pounds pressure and close at 98 
pounds. 

A safety-valve should be set by trial, to blow off at the 
required pressure as shown by a correct steam-gauge. A 
safety-valve should occasionally be lifted from its seat to 



2 66 STEAM BOILERS. 

insure that it is in proper condition. An unexpected opening 
of a safety-valve or continued leakage shows lack of attention 
to duty on the part of boiler attendants. While the safety- 
valve for a boiler should be able to deliver all the steam it can 
make, it may be considered that the proper function of a 
safety-valve is to give warning of excessive pressure. The 
safety of the boiler must always depend on the faithfulness 
and intelligence of the boiler attendants. 

The discharge of a safety-valve is often piped outside the 
boiler-room. Such pipes should be dripped to keep them free 
of water. Each safety-valve should be piped out doors separately. 

Water-column. — The position of the water-level in a 
boiler is indicated either by a water-glass or by gauge-cocks or 
by both. These may be connected directly to the front end 
of the boiler, or they may be placed on a fitting known as a 
water-column or combination. Fig. 107 shows a good form of 
water-column. It is a cast-iron cylinder connected to the 
steam-space at the top and to the water-space near the 
bottom. The normal position of the water-level is near the 
middle. There is at the bottom a globular receiver into 
which deposits from the water may settle and be blown out 
at will. 

In one side of the water-column are brass fittings for the 
water-glass, which is a strong tube of special make. The 
glass tube passes through a species of stuffing-box in the brass 
fitting. The joint is made tight by a rubber ring which fits 
on the tube and is compressed by a follower screwed onto it. 
Each fitting has a valve by which steam may be shut off when 
the tube is cleaned or replaced. A cock at the bottom drains 
water from the tube; for this purpose the lower valve is 
closed and the cock is opened. Stout wires at the side of the 
glass tube guard it from injury. 

If either valve leading to the water-glass is closed, the 
level of the water will rise in the tube. If the upper valve is 






BOILER ACCESSORIES. 



267 



closed, the steam in the upper part of the tube is gradually- 
condensed by radiation, and is replaced by water entering 
from below. If the lower valve is closed, the condensation 
of steam from radiation will accumulate and gradually fill the 
tube. 

Gauge-glasses are very brittle and, though carefully 
annealed, are under considerable stress from unequal cooling. 




WATER 
CONNECTION 



Fig. 107. 

Before a tube is put in it may be cleaned by pouring acid 
through it, or by drawing a bit of waste through on a string. 
A wire should never be forced through a glass tube, for the 
slightest scratch may start a break which will end in reducing 
the tube to small pieces. When a tube is in place it may be 
cleaned by closing the lower valve and opening the drainage- 
cock and allowing steam to blow through. 

When a boiler is left banked overnight the water-glass 



268 STEAM-BOILERS. 

should be shut off, since a breakage may result in drawing the 
•*yater in the boiler down to the level of the lower end of the 
tube. 

In addition to the water-glass, which shows at all times the 
level of the water, the water-column carries three gauge- 
cocks. One is set at the desired water-level, one a little 
above and one a little below. Steam from the steam-space, 
through the upper gauge-cock, becomes superheated as it 
blows into the atmosphere and looks blue. The lower cock 
discharges hot water from the water-space, which flashes into 
steam as it escapes, but it has a white color, which is very- 
distinct from that of the jet from the steam-space. A good 
fireman occasionally tests the position of the water-level by 
using the gauges to be sure that the indication by the water- 
glass is not erroneous. Engineers on locomotives, and boiler 
attendants where very high-pressure steam is used, often 
prefer to depend entirely on the gauge-cocks, and dispense 
with the water-glass, which may be annoying or dangerous 
when it breaks. 

The water-column shown by Fig. 107 has an alarm-whistle, 
which shows above the main casting, at the right. It is con- 
trolled by two floats inside the cylinder; one float at the top 
opens the valve leading to the whistle when the water-level 
is too high, the other near the bottom blows the whistle when 
the water-level is too low. 

If the fire is stirred up under a boiler which has had the 
fire banked, the water-level rises in the water-glass; the 
reason being that the circulation is from the front of the boiler 
to the rear, and that this circulation is maintained by a differ- 
ence of level between the front and rear ends. On the con- 
trary, the water-level falls when a boiler which has been 
steaming freely is checked. 

Steam-gauges. — The pressure of the steam in a boiler is 
shown by a steam-gauge constructed, as shown by Figs. 108, 
109, and no. The essential part is a flattened brass tube b*»nt 



BOILER ACCESSORIES 269 

into the arc of a circle as shown by Fig. 108. The section of the 
tube may be an oval, or it may have two longitudinal corrugations 
as shown by Fig. 109. 

Pressure inside of such a tube makes it bulge and tends 
to straighten it. One end is fixed and is in communication 




Fig. 108. Fig. 109. 

with the space where the pressure is to be measured. The 
other end is closed and is free to move. It is connected by 
a link to a lever which bears a circular rack in gear with a 
pinion. The motion of the free end of the tube is multiplied 
and is shown by the motion of a needle on the pinion. The 
scale on the dial is marked by trial to agree with the indica- 
tions of a mercury column or of a standard gauge. A hair- 
spring on the pinion (not shown in Fig. 108) takes up the back- 
lash of the multiplying-gear. 

The long, flexible spring-tube is liable to vibrate to an 
undue extent when the gauge is exposed to the jarring of a 
locomotive. To avoid this difficulty, two short stiffer tubes 
have their ends connected to a more effective multiplying 
device, shown by Fig. 110. The greater number of joints in 
this device makes it less sensitive than the other form. 

Since the spring-tube changes its shape if the temperature 
changes, hot steam should not be allowed to enter it. An 



270 



STEAM-BOILERS. 



inverted siphon or U tube filled with water is, therefore, inter - 
posed between the gauge and the steam from the boiler. 




U 
Fig. 1 10. 
Safety-plugs, or Fusible Plugs, as shown by Fig. in, are 
made of brass and provided with a core of fusible metal. If 
the plate into which they are screwed is in danger of over- 
heating, the fusible metal will melt and run out, and steam 
and water will blow into the furnace. If the fire is not put 
out, it will at least be checked and the attention of the fire- 
man will be attracted. 

The melting-point of fusible metals is not always certain, 
and the plugs not infrequently blow out when there is no ap- 
parent cause. On the other hand, they sometimes fail to act 
when the plate is overheated. If the plug is covered with incrus- 
tation, the fusible metal may run out without giving warning. 
The following are some of the places where a fusible plug 
is used : 

In the back head of a cylindrical tubu- 
lar boiler, about three inches above the 
top row of tubes. 

In the crown-sheet of a locomotive 
fire-box. 

In the lower tube-sheet of a vertical 
boiler; or sometimes in one of the tubes a 
Fig. in. little above that tube-sheet. 




BOILER ACCESSORIES. 



271 



In the lower side of the upper drum of a water-tube 
boiler. 

The fusible composition has a conical form so that it can- 
not be blown out by the pressure of the steam. 

Foster Reducing-valve. — When steam is desired at a 
less pressure than that of the boiler, it is passed through a 
reducing-valve like that shown by Fig. 112. The valve H is 
held open by the spring at/, acting through the toggle-levers 




Fig. 112. 

a, until the steam-pressure in the exit-pipe B, pressing 
on the diaphragm D, is able to overcome the spring and 
close the valve. The pressure at which this may occur is 
determined by the tension of the spring, which may be 
regulated by the screw at K. It is expected that the 
valve will be drawn up so as to admit just the proper 
amount of steam to the exit-pipe B to maintain the de- 
sired pressure in it. Valves for this purpose are liable to 
work intermittently, i.e. they close till the pressure falls 



272 



STEAM-BOILERS. 



below the proper point, then they open and raise the steam- 
pressure above that point. The valve is a species of throt- 
tling-valve, and therefore cannot be expected to remain tight,. 
If the machinery supplied by the reducing-valve is liable to 

be injured by excessive pressure, there must be a stop-valve 
beyond the reducing-valve. The stop-valve must be closed 
when no steam is drawn, and must be used to regulate the 
supply of steam until the amount drawn exceeds the leakage 
of the reducing-valve. 

As practically all reducing-valves make use of a diaphragm, 
or a spring, they all must give out after a certain number of vibra- 
tions of the spring or diaphragm. When a reducing-valve gives 
out there is invariably full pressure established beyond the reduc- 
ing-valve. A safety-valve large enough to take care of the 
capacity of the pipe should be placed beyond the reducing-valve. 

If high-pressure and low-pressure boilers deliver into one 
main there must be on the low-pressure main safety-valves large 
enough to take care of all the steam made by the high-pressure 
boilers. 

The Damper-regulator shown by Fig. 113 places the 
damper in the flue leading to the chimney under the control 
of the steam-pressure, so that if the pressure of the steam falls, 
the damper is opened wider to quicken the fire. The pressure 
of the steam in the boiler is communicated through the pipe a 
to the lower surface of a diaphragm, and lifts the loaded lever b, 
which stands half-way between the stops at the middle of its 
length when the steam-pressure is at the proper point. Should 
the steam-pressure rise above the proper point, it raises the lever 
and opens a small piston-valve at c, and water from a hydrant 
flows into d and presses on a piston which lifts the weights at e 
and so shuts the damper. The weighted head e of the piston is 
connected by a chain to the lever /, and closes the valve c as it 
rises, and so shuts off the water from the hydrant. 

If the pressure in the boiler drops the lever b as it descends 






BOILER ACCESSORIES. 



273 



pulls down the piston-valve in c far enough to open a dicsharge- 
port, which allows the water under the piston in d to flow to waste. 
The weights at e are made heavy enough to overhaul the 
damper and to overcome the piston friction in d. 



Ct fi t?* 1 ! 1 '"' / 




Fig. 113 



The diameter of the brass pipe d is fixed by the water-pressure 
available for working the regulator. 

Should the water-pressure fail, the regulator would not operate 
and the damper would be held open. 

Oftentimes damper-regulators are supplied with water from 
the fire-tanks located on the roofs of many of our factories. 

A regulator of the same form attached to a throottle-valve 



274 



STEAM-BOILERS. 



acts as a reducing-valve, and regulates the pressure below the 
valve with a variation of less than one pound. Fig. 114 shows 

the steam-valve used when the 
Locke regulator acts as a reducing- 
valve. The valve is a double 
valve which is nearly balanced, 
but with a slight tendency to rise 
under steam-pressure, as the lower 
valve is the larger. The cylin- 
drical part of the valve is cut into 
V notches, so that the supply of 
steam is regulated to a nicety when 
the valve is partially open. The 
cylindrical portion of the valve 
protects the valve-seat and the 
valve-face so that the valve may remain tight when closed. 

Steam-traps. — The object of a steam-trap is to drain con- 
densed water from steam-pipes without allowing steam to escape. 
As a rule a trap is placed below the pipe to be drained so that 
the drip from the pipe will run into it. Some traps that return 
the condensed water to the boiler do not conform to this rule. 

Some traps, such as the McDaniels, the Baird, and the 
Walworth, have a valve under the control of a float, which 
will allow water to pass but not steam. 




Mia 



Fig. 114. 




Fig. 115- 
The McDaniels trap is shown by Fig. 115. The drip 
enters at C and escapes through the exit at E when the valve 



BOILER ACCESSORIES. 



275 



G is open. This valve is raised by the spherical float when 
the water rises to a sufficient height. When the water is 
drained from the pipe served by the trap, the water-level in 
the trap falls and the valve G is closed. D is a counter- 
weight to balance the weight of the spherical float. The 
valve at G can be opened by screwing down the screw at A 



s ' ^\ 




Fig. 117- 
on to the counterweight. The trap can be emptied through 
the valve at F. 

The Baird trap, Fig. 116, has a spherical float D which 



L 



276 



STEAM-BOILERS. 



a ntrols a piston-valve at J. The inlet is at C, and the outlet 
at /. The screws^ and B allow the valve/ to be opened or 
closed by hand. 

The Walworth trap (Fig. 117J has a floating bucket into 
which the drip overflows after the outer case is partially 
filled. When the bucket sinks it opens a passage through 
the central spindle, and the water in the bucket is driven cut 
through this spindle. The hand-Wheel and screw at the tcp 
control a valve which is closed when the trap is working. 

The Flynn trap (Fig. 118) depends for its action on a head 
of water acting on a flexible diaphragm. Water may enter 
at the top or the bottom at ori- 
fices .marked ^4. It fills the pipe 
B and the globe C as high as 
the end of the pipe E, and pro- 
duces a pressure of about a 
pound per square inch on the 
under side of the diaphragm at 
D. The spring at G produces 
a pressure of about half a pound 
per square inch on the upper 
side of the diaphragm. Conse- 
quently the valve leading from 
the chamber F to the escape- 
pipe H is closed so long as the 
pipe E remains empty. But 
when the water overflows the 
top of the pipe E and fills the 
chamber E, the water- pressure 
on top of the diaphragm will be 
the same as that on the bottom, 
and the spring at G will open 
the valve and allow water to 
escape. If the supply of water Fig. 118. 

at A ceases, the pipe E will be emptied and the valve will be 
closed under the influence of the pressure on the under side 




BOILER ACCESSORIES. 



*77 



of the diaphragm. 




OUTLET 

Fig. 119. 



In the trap as actually constructed the 
pipe E is about 28 inches long ; in 
the figure it is made shorter in. 
proportion. 

The Curtis trap (Fig. 119) has 
an expansion-chamber at C which 
inlet is closed by a diaphragm A at the 
bottom, and is filled with a very 
volatile fluid. So long as the ex- 
pansion-chamber is immersed in 
water the pressure of the fluid on 
the diaphragm is balanced by the 
spring on the valve-spindle B. If 
the water is drained away and the 
chamber is exposed to the temper- 
ature of steam (212 F. or more), the fluid vaporizes and 
exerts enough pressure on the diaphragm to compress the 
spring and close the exit-valve. 

Return Steam-trap.— The traps thus far considered usu- 
ally discharge against the pressure of the atmosphere. They 
may discharge into a closed tank against a pressure that is higher 
than the atmosphere, but in all cases the pressure in the pipes 
drained by the trap must be higher than the discharge-pressure. 
Return steam-traps are arranged to discharge directly into the 
boiler. 

The Bundy return-trap, shown by Fig. 120, is set three feet 
or more above the water-line in the boiler. It is so made that 
it is first opened to the pipe to be drained, and fills up 
under the pressure in that pipe. It is then put in commu- 
nication with the steam-space and with the water-space of 
the boiler, and the water previously collected drains into the 
boiler. 

The trap consists of a pear-shaped receptacle or closed 
bowl, hung on trunnions, through which the bowl is filled and 
emptied. When empty the bowl is raised by a weight and 
lever; when filled with water it overbalances the weight and 



278 



STEAM-BOILERS. 



falls. The ring around the bowl limits the motion. The 
condensed water from the pipe or system of pipes to be 
drained enters the trap through the check-valve B, which pre- 
vents water from flowing back from the trap into the pipe to 
be drained. The trap is emptied through the check-valve A, 
which prevents water from the boiler from flowing into the 




Fig. i 20. 
trap. At C is a valve under the control of the trap, which 
receives steam by a special pipe from the boiler. When the 
trap is empty and is lifted by the weight and lever, the valve 
C is thrown down and is shut; water then flows in through 
the valve B from the pipe to be drained, and air escapes from 
an air-valve below C, which is open in this position of the 
trap. A check-valve on the air-pipe prevents air from en- 



BOILER ACCESSORIES. 279 

tering the trap if a vacuum happens to be formed in it. When 
the bowl is filled it falls and opens the steam-valve C, and 
steam enters the bowl through a curved pipe shown in Fig. 
120. The pressure in the bowl is now equal to that in the 
boiler, and the water collected flows into the boiler by gravity. 
Separators. — If steam is carried to a distance in pipes, a 
considerable amount of water of conden. 
sation accumulates. It is undesirable to 
have this water delivered to a steam- 
engine in any case, but if the water ac- 
cumulates in a pocket or a sag in the 
piping, it may come along with the steam 
in a body whenever there is a sudden 
change of steam-pressure, and then the 
engine will be in danger of injury. 

A good way of removing such water 
is to allow the steam to come to rest 
in a steam-drum of suitable size, from 
which the water is drained by a steam- 
trap ; the steam meanwhile may flow from 
a pipe at the top of the drum. A small 
steam-drum used as separator is likely 
to fail, from the fact that the steam does 
not come to rest, or because the entering 
and leaving currents of steam are not 
properly separated. 

The Stratton separator, shown by 

Fig. 121, brings in the steam at one side 

jjwtskjjfr of a cylinder, with a whirling motion 

Fig. 121. that throws the water onto the side of 

the cylinder; dry steam escapes through a pipe in the middle. 

A good steam-separator will remove all but one or two 

per cent of moisture from steam, even though the entering 

steam is very wet. 

Attention has already been called to the use of separators 




280 



steam-boilers. 



with some forms of water-tube boilers which do not have a 
sufficient free water-surface for the disengagement of steam. 

The three separators shown by Figs. 122, 123, and 124 may 
be used on the steam-pipe to separate water from the steam, 
or on the exhaust-pipe of an engine to collect the water and oil. 






Fig. 122. 



Fig. 123. 



Fig. 122 represents the Curtis baffle-plate separator. The 
entering steam is divided into three portions, which flow as shown 
by the arrows. 

Water or oil coming in contact with the plates adheres to the 
plates and is collected in the space at the bottom. 

The Triumph separator, shown by Fig. 123, removes oil or 
water by centrifugal action and by a settling-chamber. The 
direction of flow is shown by the various arrows. 

Fig. 124 illustrates the Detroit separator. The steam is 
directed against a corrugated annular plate to which water and 






BOILER ACCESSORIES. 



28l 



oil adheres. A settling-chamber in the shape of an enlargement of 
the casting allows floating particles to be deposited by gravity. 

Tests made with these separators connected to the exhaust- 
pipe of an engine have shown that by their use 80 per cent of the 
cylinder oil used in the engine may be taken out of the exhaust. 




Fig. 124. 

Most of this oil is mixed with water in such a way that it cannot 
be separated from the water. 

Oil-filters. — If exhaust steam is used for heating and the 
condensation in the system is returned as feed-water to the boiler 
it is of great importance that this water should be free from oil. 

An oil-separator will take out 80 per cent of the oil. The 
greater part of the 20 per cent remaining may be taken out by 
a straw-filter. 

The returns from the heating system are passed through a 
box about 8 feet long and 2 feet square in section, open at the 
top. There are partitions across the box so that the water enter- 
ing at one end flows over one partition and under the next, over 
the third, and so on. 

The entire box is filled full of hay or straw. Water is taken 



282 



STEAM-BOILERS. 



into the feed-pump from the opposite end of the box. If this 

straw is changed once in two weeks, or oftener if necessary, not 

enough oil will get into the boilers to cause any trouble. 

Feed-water Heaters. — The feed-water supplied to a boiler 

SAFETY " 
VALVE rt fcsi BLOW-OFF 



FEED TO 

BOILER 







u 

MUD BLOW OFF 

Fig. 125. 

may be heated up to the temperature of the exhaust-steam by 
passing it through a feed-water heater. Feed-water heaters 
are sometimes made open, i.e., the steam from the engine 



BOILER ACCESSORIES. 



283 



mingles with and heats the feed-water. Such heaters have 
the disadvantage that the oil from the engine is carried into 
the boiler. 

A closed feed-water heater resembles a surface condenser, 
and as the steam and water do not mingle, there is no danger 
of carrying oil from the engine into the boiler. The Wain- 
wright heater, shown by Fig. 125, has the heating-surface of 
corrugated copper or brass tubes, of peculiar make, to allow 
for expansion. The steam from the engine passes around 
the tubes and the feed-water passes through the tubes. 

The Berryman feed-water heater, shown by Fig. 126, is 
arranged to have the exhaust-steam pass 
through a series of inverted U tubes, 
around which the feed-water circulates. 
Live-steam feed-water heaters take 
steam from the boiler to raise the tem- 
perature of the feed-water up to, or 
nearly to, the temperature in the boiler. 
The principal advantage appears to be 
that unequal contraction, due to the in- 
troduction of cold water, is avoided. It 
is claimed that with some forms of 
boilers a better circulation is obtained 
by aid of such a heater. 

The use of a feed-water heater for 
removing lime-salts from feed-water has 
been discussed on page 73, and an ex- 
ample of such a feed-water heater was 
illustrated in connection therewith. 
Feed-pipes. — The temperature of 
—r\ the feed-water is usually much below 
II — ^ the temperature in the boiler. It thus 
becomes essential to so locate the inlet, 
and to so distribute the water, that un- 
due local contractions may not occur; this is of special im- 




MUD PIPE 

Fig. 126. 



284 STEAM BOILERS 

portance when the supply is intermittent. The feed-pipe for 
the cylindrical tubular boiler, shown by Plate I, enters che shell 
near the water-line, through the front head. It is carried 
along one side of the boiler for about three fourths of its length, 
and then is carried across over the tubes and opens downward. 
A feed-pipe is often perforated to give a better distribution of 
the feed-water. 

The shell is reinforced by a piece of plate riveted on the 
outside, where the feed-pipe enters the boiler. The end of 
the pipe has a long thread cut on it, so that it can be secured 
through the reinforcing-plate and the boiler-shell, and may 
then receive a pipe-coupling which connects it to the continu- 
ation of the feed-pipe inside. 

Sometimes the feed-water is delivered to an open trough 
inside the boiler, .from which it overflows in a thin sheet. 
Or a perforated pipe may deliver the water in form of spray 
in the steam-space. Either method has the advantage that the 
water comes in contact with steam and is heated before it 
mingles with the water in the boiler. There is the disadvan- 
tage that the steam-pressure may fall off when the feed-water 
is turned on or is increased. 

It has already been pointed out that the feed-pipe should 
have a globe valve near the boiler, and a check-valve between 
the globe valve and the feed-pump. 

Feed-pumps. — Boilers are commonly fed by a small direct- 
acting steam-pump placed in the boiler-room. The steam- 
consumption per horse-power per hour of such pumps is very 
large, and yet the total steam used is insignificant. They are 
cheap and effective, and easily regulated. 

If the boiler-pressure is over 100 pounds an outside packed 
plunger is preferable to a piston-pump. 

The pump should be of the duplex type and the plungers at 
the water end should be covered with a composition or brass 
sleeve. 

Power pumps driven from a large engine are more econom- 






BOILER ACCESSORIES. 285 

ical, provided their speed can be regulated; they not infre- 
quently are arranged to pump a larger quantity than required 
for feeding the boiler, the excess being allowed to flow back to 
the suction side of the pump through a relief -valve. 

When one pump supplies several boilers, a series of diffi- 
culties is liable to arise. First, if the boilers are fed singly 
in rotation, the Large intermittent supply of feed-water is 
likely to give rise to local contraction and the water-level in 
the boiler fluctuates; there is liability that the water-level will 
fall too low, endangering the heating-surface, or there may be 
excessive priming when the water-level is high. It appears 
advisable that the feed should be delivered to all the boilers 
simultaneously, the supply to each boiler being regulated by 
its stop-valve; each branch pipe to a particular boiler should 
be provided with its own check-valve, and the water-level and 
rate of feeding of each boiler must be carefully watched by 
the fireman, or by a water-tender if there are many boilers. 

Injectors. — An injector is conveniently used for feeding a 
boiler if the feed-water is not too hot ; it has the incidental advan- 
tage that it heats the water as it feeds it into the boiler. An 
injector should be connected up with unions, so that it may 
readily be taken down for inspection. At sea an injector is com- 
monly used when the boilers are fed from the sea or from a supply- 
tank. 

Every boiler should have two independent sources of supply 
of feed-water, so that there may be some resource if the usual 
supply gives out. There may be two pumps, or a pump and an 
injector. A locomotive usually has two injectors. 

As the amount of water delivered by an injector can be varied 
only by a small amount, and as an injector has to be large enough 
to supply a boiler at the time of maximum demand, it follows 
that under the ordinary working conditions of the boiler the 
injector must be used intermittently. 

Fig. 127 illustrates a Koerting injector. This injector has 



286 



STEAM-BOILERS. 



two sets of tubes; the lower or lifting-tube and the upper or 
forcing-tube. 

After opening the steam-valve in the pipe S the injector is 
started by pulling the handle about i^ inches to the left. This 
uncovers the lower steam-nozzle or lifting-nozzle. 




Fig. 127. 



As soon as water appears at the overflow O, the handle is 
pulled back as far as it will go. This, after opening the lower 
steam-nozzle wide open, opens the upper steam-nozzle, and at the 
same time pushes down the overflow -valve through a link running 
along the side of the injector. It will be noticed that the water 
must meet with considerable resistance in passing through the 
various passages in the injector. 

Blow-off Pipe. — The blow-off pipe draws from the lowest 
part of the boiler, or from some place where sediment may be 
expected to collect. On the blow-off pipe there is a cock ox 
a valve which is opened to blow out water from the boiler. 
Sometimes there are both a cock and a valve. A cock has 
the disadvantage that it may give trouble by sticking; a valve 
may leak and the leak may not be detected. 






BOILER ACCESSORIES. 



287 



The pipe should be carried beyond the cock, so that the 
attendant is not liable to be splashed with hot water, but the 
pipe should end in the boiler-room or where discharge through 
the pipe on account of a leaky cock or valve may be sure to 
attract attention. Each individual boiler should have its own 
blow-off pipe. 

The blow-off pipe where it passes through the back con- 
nection is covered with magnesia, asbestos, or fire-brick. In 
spite of this protection the blow-off pipe may burn off. The 
device shown by Fig. 128 is used to overcome this difficulty. 



WATER LINE 



^ 



Fig. 128. 

When the blow-off cock is shut and the valve on the vertical 
branch is open, there is a continuous circulation of water 
which keeps the pipe from burning. The valve on the verti- 
cal branch is closed before the blow-off cock is opened. 

If a blow-off pipe burns off and water begins to escape, the 
feed-pump should be run at lull capacity to keep water in the 
boiler and guard the plates trom burning, if that is possible. 
The fire should then be checked by throwing on wet ashes or 
by other means, unless escape of steam from the break in the 
blow-off pipe prevents. 



288 



STEAM-BOILERS. 



Piping to carry steam from a boiler to an engine, for 
heating buildings- and for other purposes is too important to 
be considered as accessory to the boiler. A lew remarks, how- 
ever, may not be out of place- 

The coefficient of expansion of steel pipe is .0000065. This 
means that for each degree increase in temperature the pipe 
expands this fraction of its length. 

Thus a pipe at 70 F. measures 100 feet. What will be the 
expansion of this pipe if used to carry superheated steam at 165 
pounds absolute pressure with 150 superheat? 

At 165 pounds absolute the temperature is found from the 




O-Six % holes 

14 W BALANCED EXPANSION JCINT 




Fig. 129. 

tables to be 365 . 9 F.; add 150 to this, giving 5i5 G .o. as the tem- 
perature of the steam. The increase of temperature is 515.9 — 70 

or 445°-9- 

445 . 9 X. 000006 5 X 100' X 1 2" =3.48" 

the expansion in the 100 feet. 

In a long line of high-pressure piping where the expansion is 
6 or more inches, the expansion may be taken up in an expansion- 
joint like that shown by Fig. 129. The flanges at either end are 
connected to the pipe. 



BOILER ACCESSORIES. 289 

The drawing needs no explanation. 

An expansion-joint, like Fig. 129, is in use on a 20-inch pipe 
at the Merrimack Mills at Lowell, Mass. The following figures 
on expansion were obtained by the chief engineer: 

Length of 20-inch and 16-inch pipe, 277 feet 8 inches. 
Temperature of outside air, 56 F. 
Expansion of the pipe at 50 pounds gauge, 4j-| inches. 
At 100 pounds gauge, 5}--?- inches. At 150 pounds gauge, 
6J-| inches. 

In long runs of pipe not over 6 inches in diameter, the expan- 
sion may be allowed for by screwed fittings, as shown by Fig. 130. 




Fig. 130. 

The pipes shown broken are anchored at either end. The 
length of the pieces running at right angles depends upon the 
amount of expansion to be taken care of. 

As arranged there is no chance to pocket water in the expan- 
sion-joint. A drip should be provided at the end of the pipe 
bringing steam into the joint. 

A common way of allowing for expansion is illustrated by 
Fig. 131, which shows the connection from a boiler to the main 
steam-pipe. When the main steam-pipe expands or contracts, 
the short nipple between it and the angle-valve turns a little at 
one or at both ends; in like manner the vertical pipe turns a 
little at the nozzle or at the elbow. The motion is so small and 
so distributed as not to give any trouble unless the expansion to 
be provided for is very large. 



290 



STEAM-BOILERS. 



Fig. 131 is so arranged that there is no space where water 
can collect when the boiler is shut off from the main steam- 
pipe. If the stop-valve were in the vertical pipe, as is some- 
times the case, then the pipe over the valve would fill up with 
water when the boiler is shut off, and that water would be 



O 





Fig. I3 1 - 



suddenly blown into the steam-main when the stop-vaive is 
next opened. A pipe so situated should always have a drip- 
pipe to draw off condensed water before the valve is opened. 
As a special example we may mention the pipe leading to an 
engine, which always has a drip-pipe above the throttle-valve. 
Pipes that are likely to be troubled by condensation should 
be continuously drained by a steam-trap. 

Horizontal pipes are sometimes arranged so that water may 
collect in them, due to a sag in the pipe or to the fact that 
they do not properly drain through a side branch. Though 
the water may lie quiet in such a pocket while the draught of 
steam is steady, a sudden increase in the velocity of the steam, 
or a rapid opening of the valve supplying steam to the pipe, 
will sweep the water up and carry it along with the steam. The 
danger from the inrush of water to an engine is readily seen, 
but it is not so well known that the water thus violently thrown 



BOILER ACCESSORIES. 291 

against elbows and other fittings give rise to leaks, if it does not 
burst the fittings. It is to be remembered that steam offers 
little or no resistance to the movement of water in a pipe, as it 
is readily condensed either from a slight increase of pressure 
or by mingling with colder water. Again, water at the temper- 
ature corresponding with the pressure easily separates, forming 
bubbles of steam, which as easily collapse, and the shock of 
impact of the water gives rise to pressures that search out 
all weak places in the pipe, even at some distance. 

Steam-piping should be pitched in the direction of the flow 
of the steam sufficiently to drain out the condensation. 

Should a large pipe be connected to one of smaller diameter, 
the bottom of the inside of the pipes must be kept on the same 
level. For this purpose eccentric flanges and tees with eccentric 
outlets may be used. 

To-day nearly all of -the high-pressure piping is put up with 
elbows made of bent pipe instead of cast-iron or gun-iron flanged 
fittings. The bent pipe, by giving, allows for expansion, and it 
also reduces the friction loss in passing through the quarter turn. 
The radius of the bends is commonly made equal to five diam- 
eters of the pipe. 

To get some idea as to the stiffness of these bent pipes the 
following tests on bent pipes were made at the Massachusetts 
Institute of Technology by two seniors under the direction of one 
of the writers: 

The figures marked Pipes Nos. 1-9 give the size and weights. 
The load was applied at the points marked by the arrows, and 
deflections were measured at points indicated by the dash and 
dot lines. 

Fig. 132 illustrates the best practice in connecting a boiler to 
the main. The pipe is given a slight pitch towards the main. 
There are two straight-way valves with advancing stems and a 
blanked tee in the line. The three may be bolted together. 
The valve operated by the chain has a by-pass (not shown). 

If a boiler is piped to the main in this way there is no danger 



292 



STEAM-BOILERS, 





r *■— — 73 —j t 

Weight = 552 lbs. Outside dia. 6.625 " Inside dia. 6.065 





-a 
"Weight =133 lbs. Outside dia.3.500, Inside dia. 3.067 





BOILER ACCESSORIES. 



293 



PIPE No. 1. 
Outer dia. 5". Inner dia. 4.25' 



PIPE No. 2. 
Outer dia. 6.625". Inner dia. 6.065' 





Total Motion in Inches. 


Load, 
Pounds. 




At Outer 
Line. 


At Inner 
Line. 


200 


.060 .025 


400 
600 

800 


- I2 5 
.185 

.250 


.050 

.076 

I05 


1000 
1200 


-3" 

-37 2 


133 
.160 


1400 
1600 
1800 
2000 


-435 
•499 
.561 
.625 


-185 
.213 
.240 
.265 





Total Motion in Tnches. 


Load, 
Pounds. 




At Outer 


At Middle 


At Inner- 




. Line. 


Line. 


Line. 


600 


.29 


.16 


.08 


1200 


-58 


-31 


.16 


1800 


.87 


-45 


2 3 


2400 


1. 16 


.61 


3i 


3000 


I-50 


.78 


•39 


3600 


1.88 


.96 


.48 



PIPE Nd. 3. 
Outer dia. 6.625". Inner dia. 6.065". 





Total Motion in Inches 




Load, 
Pounds. 










At Outer 


At Second 


At Third 


At Inner 




Line. 


Line. 


Line. 


Line. 


200 


1 . 20 


0.83 


0.50 


0.17 


400 


2 


35 


1-65 


0.97 


0-34 


600 


3 


55 


2-45 


i-45 


0.80 


800 


4 


70 


3-3° 


i-95 


O.67 


1000 


5 


90 


4-15 


2-55 


O.86 


1200 


7 


3° 


5.20 


3.20 


I 10 


1400 


9 


i5 


6.50 


4 .oo 


I -50 



PIPE No 4. 
Out. dia. 6.625". In. dia. 6.025". 





Total Motion 
in Inches. 


Load, 
Pounds. 




At Outer 
Line. 


At Inner 
line. 


IOOO 


.050 


-OI5 


2000 


. 107 


.030 


3000 
4000 
5000 
6000 


.167 

- 2 3° 
-293 
-365 


-045 
.060 
.080 
. 100 


7000 


.442 


.123 


8000 
8500 


-542 
.603 


-155 
.174 



PIPE No. 5. 
Outer dia. 5.563." Inner dia. 5.045' 



Load, 
Pounds. 


Total Motion in Inches. 


At Outer 
Line. 


At Inner 
Line. 


IOOO 

2000 
3000 
35°° 


- 2 °5 
.407 
.612 
.740 


.058 

-115 
.177 
.216 



294 



STEAM-BOILERS. 



PIPE No. 6. 
Outer dia. 8.62". Inner dia. 7.62' 



PIPE No. 7. 
Out. dia. 7.625". In. dia. 7 023' 



Load, 
Pounds. 


Total Motion in Inches. 


At Outer 
Line. 


At Middle 
Line. 


At Inner 
Line. 


1000 

2000 
3000 
4000 
5000 
6000 
7000 
8000 
8500 


-175 
-345 
-5i6 

-695 

.860 

I.032 

I 206 

1 375 
1.463 


.108 
217 
•324 
-435 
•542 
.652 
.761 
.872 
-932 


050 
. 100 
.151 
•205 
-255 
■3°7 
.360 
.410 
.440 



PIPE No. 8. 
Out, dia. 3.500". in. dia. 3.067' 



Load 
Pounds. 


lotal Motion in Inches. 


At Outer 
Line. 


At Middle 
Line. 


At Inner 
Line. 


100 
200 
300 
400 


820 
1.620 
2. .420 
3.280 


.441 

.880 

1.320 

1. 912 


.124 
.248 

.380 
.560 



Load, 
Pounds. 


Total .Motion 
in Inches. 








At Outer 


At laner 




Line. 


Line. 


1000 


.182 


.080 


2000 


•390 


.160 


3000 


.628 


- 252 


4000 


.892 


.366 


5000 
5500 


I.225 
I.480 


.5IO 
.618 



PIPE No. 9. 
Out. dia. 3.500". In. dia. 3.067". 





Total Motion in Inches. 


Load, 












At Outer 


At Inner 




^me. 


Line 


200 


-158 


■037 


400 


-3 11 


.071 


600 


.466 


.106 


800 


.620 


.142 


1000 


•775 


.178 


1200 


-950 


.228 


1400 


1. 215 


3 J 9 




Fig. 132. 

in going inside the boiler even though there may be 200 pounds 
pressure in the main. By shutting both valves and uncovering 



BOILEF ACCESSORIES. 



2 95 



the outlet on the blanked tee there is no possibility of steam 
leaking back into the boiler. 

The outlet of the tee may be on the side or on the bottom. 
Piping must be anchored at some point. Generally there 
must be an anchorage near the engine. Each system of piping 
has to be considered by itself, and no general rule can be given. 
A simple form of anchor is shown by Fig. 133. If a pipe 
passes through a brick wall a clamp may be made to fasten to the 
pipe and to bear against the wall. 

Fig. 134 shows a method used in supporting large pipes. The 
top roller is generally omitted. 

Small piping, up to 8 or 10 inches, is frequently hung by 
rings. 

Figs. 135, 136, and 137 show three of the forms of flanged 
joint used on high-pressure piping. Fig. .137 is known as the 
Van Stone joint. 

Bursting Pressure of Extra Heavy Flanged Fittings. — 
— An investigation as to the strength of fittings was made by the 
Crane Company and the results of their tests published in The 
Valve World of Nov., 1907. From their tests they deduced the 
following formula: 

T = thickness of metal; 
D = inside diameter; 
B = bursting point; 

5 = 65 per cent of tensile strength of the metal up to 12 
inches diameter and 60 per cent for sizes over 12 
inches diameter. 



T 
3 XS=B. 



For working pressure divide B by a factor of from 4 to 8 as desired. 
Vibration of Steam-pipes. — Steam pipes-connected to high- 
speed engines seldom vibrate much. Pipes leading to slow- 
speed engines often vibrate badly. 



196 



STEAM-BOILERS. 




Fig. 133. 




Fig. 134. 




Fig. 



1 35- 




Fig. 136. 




Fig. 137. 



BOILER ACCESSORIES. 



•97 



An engine, rigid on its foundation, may set up vibrations in a 
pipe through pulsations caused by the checking of the velocity of 
the steam at cut-off. Such vibrations are most apt to oocur in 
pipes which are amply large for the engine. 

In most cases of vibration, if the stop-valve on the boiler is 
closed so as to make a slight drop in pressure at the engine, 2 
or 3 pounds, the vibration will cease. A large drum placed close 
to the engine with a throttling-valve in the steam-pipe enteri -g 
the drum will accomplish the same result. The valve close to 
the drum will then be used to stop the vibration 

Area of Steam-pipe. — In order chat the loss of pressure 
in a steam-pipe due to friction may not be excessive, it is 
customary to limit the velocity to 5000 or 6000 feet per min- 
ute. If there are many bends or elbows in the pipe, the 
velocity may be 4800 feet per minute, or less. 

Example. — Required the diameter of the main steam-pipe 
leading from a battery of boilers having an aggregate of 3000 
boiler horse-power. Assume the pressure to be 100 pounds 
by the gauge, or about 115 pounds, absolute. Assume also 
that a boiler horse-power is equivalent to 30 pounds of steam 
per hour. Then the steam drawn from the boiler in one hour 
is 

30 X 3000 = 90,000 

pounds. The steam per minute is consequently 1500 pounds. 
Now one pound of stearr. at 115 pounds absolute has a 
volume of 3.862 cubic feet. Consequently 

1500 >( 3.868 =5802 

cubic feet of steam per minute must pass through the steam- 
main. With a velocity of 5000 feet per minute the area of 
the pipe must be 

5802 -4- 5000 =1.16? 



298 STEAM-BOILERS. 

square feet, or 167.0 square inches. The corresponding diameter 
is 14^ inches. The next larger size of pipe is 16 inches, which 
will be used. 

In calculating the size of the steam-pipe needed for a battery 
of boilers the lowest pressure at which the boilers will ever work 
must be considered, for a pipe which will carry 500 H.P. at 150 
pounds pressure will carry only about 3/4 of 500 at 100 pounds 
pressure with the same velocity. 

Flow of Steam in Pipes. — Various formulae have been 
proposed for use in figuring the weight of steam a pipe will deliver 
with a cretain drop in pressure. 

An article by Prof. G. F. Gebhardt in Power, 1907, compares 
all of these formulae. 

It would seem that the formulae proposed by Mr. G. H. 
Babcock give results which agree very closely with results ob- 
tained by experiment. 
In this formula 

- w = the weight of steam in pounds per minute; 
d = diameter of pipe in inches; 
L — length of pipe in feet ; 

P = the drop in pressure in pounds per square inch; 
y = the mean density in pounds per cubic foot ; 
V = velocity in feet per minute. 



F = I5,950 



>|Wi+ 



3.6V 



o Pyd 5 
^=87 



P-. 00013 2 1 






^~d 
yd 5 



BOILER ACCESSORIES* 



299 



Pipe-covering. — The steam-pipes should be covered with 
some non-conducting material to prevent radiation of heat. 
Magnesia, asbestos, mineral wool, hair-felt, etc., have been us^.d 
for such coverings. 

Generally a sectional covering is used on the straight pipe and 
plastic on the fittings. 

It is probable that four tenths of a heat-unit will be lost per 
square foot of pipe surface per hour per degree difference of 
temperature between the steam inside the pipe and the air, if any 
good covering from 1 inch to i\ inches in thickness is used. A 
bare pipe would lose from 2.5 to 3 heat-units in radiation from 
each square foot per hour and per degree difference of temperature. 
The saving to be made by covering the pipes is apparent. 

Tube-cleaners. — To remove the scale which collects on the 
inside of the tubes of water-tube boilers supplied with a poor 
grade of feed-water, turbine tube-cleaners are used. 

Figs. 138 and 139 show the Liberty tube-cleaners. The head, 




Fig. 138. 



shown by Fig. 138, is for hard scale, and also for use in a bent 
tube. 

Fig. 139 shows a different head attached to the turbine. The 
turbine blades are seen in Fig. 139. Water from a hose is taken 
into the outer casing. The water in escaping passes through 
the turbine, which rotates at high velocity, throwing the arms 
with cutters out by centrifugal force. The scale removed is 
washed away by the water. 

The Weinland turbine cleaner is shown by Figs. 140 and 141. 



3°° 



SI E AM -BOILERS. 




Fig. 139, 




Fig. 140. 







Fig. 141. 




Fig. 142. 



BOILER ACCESSORIES. 301 

The lower right-hand figure is in section. The porcupine head 
which is used on heavy scale, is shown at the left. 

This, like the preceding, operates with a ij-inch hose. 

A cleaner for removing soot from the inside of fire-tubes is 
shown by Fig. 142. This is attached to a long rod and pushed 
through the tube. 

Coal Conveyers. — Two types of coal-conveyers are used 
for elevating coal from the ground to the hoppers supplying the 
boilers or to the coal-pocket; the iron bucket conveyer and the 
belt-conveyer. Fig. 143 shows a bucket-conveyer and the method 




r-) o O o o O 0^0 o 0^0 O o o o ° °6 




Fig. 143. 

of driving it. The buckets are joined together by an endless 
chain made of links supported by flanged wheels on a track. The 
buckets are free to swing about their point of attachment to 
the links. 

The driving-gear carries a number of pawls which are so 
guided at their inner ends by a fixed cam that each in succession 
pushes on pins or studs projecting from the link-chain. 

The conveying-buckets swing freely on pivots, so thLt it is 
necessary to load them evenly to prevent tipping. This loading 
is accomplished by the filler, Fig. 144. It has a series of bottom- 
less shells which fit the buckets of the conveyer. It also prevents 
coal from dropping between the buckets as they are filled. The 
filler is driven by the conveyer. 



302 



STEAM -BOIL^S. 



A set of rolls, such as is used for supporting a 24-inch belt on 
a belt-conveyer, is shown by Fig. 145. Sets of rolls are placed 



close together. 







Fig. 144. 

The end rolls of each set are inclined so that the carrying side 
of the belt is bent into an arc of a circle. Soft coal has been 
elevated at an angle of 17 without rolling. 




^5 



Fig. 146. 

A distributing tripper is shown by Fig. 146. 
The conveying belt brings the material from the left as shown 
in the cut and passes over roller B and then over C and passes 



BOILER ACCESSORIES. 303 

along to the right. As the belt goes over B the material on it is 
dumped through the chute of the tripper. The tripper is set 
on a truck (D) which moves on a track. It is moved by means 
of a clutch, regulated by handle A, which puts the gear E into 
connection with B or C, which are revolving in opposite direc- 
tions. The tripper may be set so as to discharge over any space 
desired. The handle A, by striking against dogs placed at either 
end of the travel of the carriage, automatically shifts the clutch 
driving the gear E and causes reversal. 



CHAPTER X. 
SHOP-PRACTICE. 

The method of work in a boiler-shop depends on the size 
and arrangement of the shop and on the class of work. 
There are, however, certain general principles which can be 
recognized in all modern shops. 

The materials, especially the plates, are received at one 
end of the shop, near which is a storeroom, and a bench for 
laying out work. The plates, after they are laid out, pass in 
succession to the several machines, where they are sheared, 
punched or drilled, planed, rolled, and riveted. The machines 
for performing these operations are arranged in order with 
proper spaces for handling and working. Space is provided 
where boilers may be assembled and receive their tubes and 
furnaces. Machines which, like the punch, have much work 
to do, compared with other machines, may be duplicated. 

There should be an efficient system for handling the 
material at the machines and for passing it on from one 
machine to the next. A good arrangement is to have a 
swing-crane near each machine ; the spaces served by the 
several cranes overlap, so that one crane takes material from the 
next, and so on. It is advantageous, especially in large shops, 
to have a travelling crane that can handle the largest boiler 
made, and which can serve any part of the shop. 

Flanging and smithing are usually done in a separate shop 
or room. A few machine-tools are needed for doing work on 
steam-nozzles, manhole rings and covers, etc. 

A boiler-shop will have an office, a drawing-room, and a 

3°4 



SHOP-PR A C PICE. 305 

pattern-room, also a storeroom for patterns. These may be 
conveniently located in the second story. 

A Boiler-shop. — The application of the general princi- 
ples just stated and the explanation of details can be best 
given by aid of an example. A medium-size shop for making 
cylindrical boilers has been chosen for this purpose; the 
shop is capable of making any shell boiler of moderate size. 
This shop will employ sixty or seventy men and can turn out 
two 100-horse-power boilers per day. It will take about 
three days to finish one boiler, so that there may be six or 
more boilers in process of construction at one time. 

The shop which is represented by Fig. 147 has one end 
on the street and has a driveway or yard at one side. Plates 
are received at the street-door by a travelling crane and stored 
near at hand. The same crane takes plates to the laying-out 
bench and from there to the crane which serves the shearing- 
machine. Along one side of the shop are arranged in suc- 
cession a shearing-machine, two punches, a plate-planer, a 
set of plate-rolls, and a riveting-machine. Between the 
punches and nearer the wall is a flange-punch ; near the 
planer is a forge for scarfing. This series of machines is 
served by four swing-cranes, and there are also two hydraulic 
cranes near the riveting-machine. These cranes, which are at 
the top of a tower thirty feet high, are operated from the 
working platform of the riveter. There are two shipping- 
doors where the finished boilers are delivered to teams, and at 
each door there is a jib-crane for handling the boilers. These 
jib-cranes and the hydraulic cranes at the riveter have a 
capacity of eight or ten tons ; the swing-cranes may be much 
lighter. A shop where large marine boilers are made will 
have more powerful cranes. 

The machine-shop is near the receiving-door. Here are 
the lathes, planers, and drills for doing work on manholes, 
nozzles, and other fittings ; also a bench for fitting up boiler- 
fronts. Two drills for boring tube-holes in tube-plates, and 



3° 6 



S TEA M-B OILERS. 







2 £ 






J.33U1S 



SHOP-PR A CTICE. 307 

a boring-mill for facing off the flanges of boiler-heads, are 
placed in the entrance to the machine-shop, where work can 
be conveniently brought to them from the boiler-shop. At 
the end partition of the machine-shop are places for storing 
boiler-front castings and sheet-iron. The corner of the boiler- 
shop near the machine-shop is known as the cold-iron shop ; 
here the uptakes, flues, and dampers are made. This shop 
has a shearing-machine, three punches, and a set of rolls 
suitable for sheet-iron work; also a bench with hand-vises. 

At the rear of the boiler-shop there is in one corner a store- 
room for tubes, stay-rods, channel-bars, and finished fittings. 
In the opposite corner are the forge-shop and the engine- 
room. These are separated from each other and from the 
boiler-shop by glass partitions which do not cut off the light, 
and yet keep the smoke and dust from the forge out of the 
other rooms. 

The main line of shafting is near the wall over the shear- 
ing-machine, punches, and rolls. The shafting for the ma- 
chine-shop and cold-iron shop is driven by a belt from the 
main shaft, near the front end of the building. A space is 
left near the riveter where the plates from the rolls can be 
assembled rnd bolted together before going to the riveter. 
In front of the riveter there is a space about 60 feet wide 
and 120 feet long where boilers are deposited after leaving 
the riveter. Here the boilers receive their stays and tubes, 
here they are calked and receive all fixtures that are perma- 
nently attached to the shell. At this place the boilers are 
tested by hydraulic pressure, usually to one and a half times 
the working pressure. When complete the boilers are painted 
and oiled, ready for shipment. 

To illustrate the method of building a boiler more in 
detail, the different steps in making a horizontal boiler will 
be followed in order. 

Flanging Heads. — Regular sizes of boiler-heads flanged 
at one operation by machinery can now be bought on the 



3 08 S TEA M-B OILERS, 

market, and all except the largest shops are in the habit of 
buying them. The flanging-machine has a former and a die 
between which the plate is formed under hydraulic pressure 
while at the proper flanging temperature. No strains due to 
unequal heating or cooling are set up in this process, and 
the plate, which is allowed to cool gradually, does not need 
to be annealed. 

Irregular sizes and shapes are made in the shop on a 
special cast-iron anvil, which is about six inches deep, flat on 
top, and curved at one side to about the radius of the head to 
be flanged. The corner of the anvil or former is rounded so 
as not to cut the plate. It is placed near a special low forge 
where the plate is heated. 

In flanging, the plate is first marked at short distances on 
the inner circle of the bend with a prick-punch. A portion 
of the plate is then heated to a good heat, and the plate is 
taken to the anvil or former. After adjusting so that the 
depth of flange overhangs the right distance from the edge 
of the former, the heated portion of the plate is beaten down 




Fig. 148. — Lifting-dogs. 

against the side of the former by wooden mauls and then 
smoothed with a flatter and sledge. The plate is then heated 
in a new place and another portion bent. To straighten the 
head and also to remove the strains set up by this way of 
flanging, it should be heated to a dull red and allowed to cool 
gradually. 

The lifting-dogs represented by Fig. 148 are used in lift- 



SHOP-PR A CTICE. 



30Q 



ing and placing the head during the flanging, and in handling 
plates during other operations. 

Fig. 149 represents crane-lifts which are used when plates 
are lifted and carried by cranes. 




CRANE LIFTS 

Fig. 149. 

After the head is flanged, holes for rivets, stay-rivets, 
and tubes are marked, and all the rivet-holes are punched. 

Flange-punch. — The holes in the flange are punched by 
a special machine shown by Fig. 150. The punch is carried 




Fig. 150. 

by a horizontal wrought-iron plunger which is operated by a 
cam. The die is carried by a hooked extension of the frame. 
The head is held horizontal with the flange down ; the flange 
is dropped between the punch and the die and the lever is 



3io 



S TEA M-B OILERS. 




Fig. 151. 



pulled to throw the cam into play ; the plunger then makes 
a stroke and punches a hole. The machine is driven by a 
belt, with a fast-and-loose pulley. On the shaft with these 
pulleys is a heavy fly-wheel. A pinion and spur-gear give a 
slow powerful stroke to the gear which moves the cam. 

Punch and Holder. — The punch (Fig. 151) is made of a 
solid piece of tool-steel. It has a flat head and a conical 

shoulder by which it is held onto 
the plunger, a short straight body, 
and a slightly coned point. The 
> point is larger at the cutting edge 
than back toward the straight 
body, to avoid friction in the hole. 
A tit in the middle of the face of 
the punch catches in the centre- 
punch mark and centres the hole punched. 

The holder is made of wrought iron. It screws onto the 
end of the plunger, grips the punch by the conical shoulder 
on its head, and draws it down firmly against the plunger. 
Tube-holes. — There are two ways of cutting the holes 
for the tubes in boiler-heads. Some- 
times a small hole is punched at the 
centre of the hole. A tool like that 
shown by Fig. 118 is then put in the 
drill-press. The post in the middle is 
run through the small hole previously 
punched or drilled, and the two cutters 
rapidly cut out the tube-hole to the 
proper size. 

The other way is to 
punch the tube-holes 
at once to the proper 
size by a helical punch 
shown by Fig. 119. The die is made in the form of a ring 
with a flat face, so that the punch begins to cut at the cor- 



riR 



V 




Fig. 152. 



Fig. 153. 



SHOP-PR A CTICE. 3 1 1 

ners, and the metal is removed by a shearing cut. Though 
not always done, the holes ought to be punched a little under 
size and then reamed out to give a fair surface against which 
the tubes may be expanded. 

Finishing the Flange. — The boiler-heads are placed on 
the platen of a boring-mill like that shown by Fig. 154, and 
the edge of the flange is turned off. The heads of marine 
boilers are often turned to a true cylinder at the flange to insure 
that they shall exactly fit the cylindrical shell into which 
they are riveted. This also gives a good surface to calk 
against. 

Boring-mill. — A simpler machine than the boring-mill 
shown by Fig. 154 would answer to turn off the flanges of 
the boiler-heads. But the machine is useful in other ways 
and may do the work wfn^h is commonly done on a large 
lathe. 

The platen is driven much in the same manner as the 
head of a lathe, through gearing and cone pulleys, to provide 
for various speeds. This gearing is not well shown in the 
figure, as it is hidden by the frame. The cutting-tool is ad- 
justed and controlled much like the tool of a planer. The 
tool-carriage is on a horizontal cross-head which is supported 
at the side frame and on a round vertical bar at the middle. 
The tool can be traversed in and out on the cross-head, and 
the cross-head may be raised or lowered. 

For doing some classes of work the cross-head may be 
set vertically on the guides that are shown on the horizontal 
bars of the frame near the right-hand end. Or, again, a tool 
may be carried by the central rod, which can be fed down by 
the screw at the top. 

Laying on the Plates. — The first and one of the most 
important steps in the work on the shell is the marking out 
of the plates. Generally one man in each shop does all the 
laying out. After squaring the sheet, he marks off the 
length and locates the rivet-holes by means of gauges. These 



312 



S TEA M-B OILERS. 



gauges have to be made by trial, a suitable allowance being 
made in them on account of the thickness of the plate for the 




Fig. 154. 
change in length due to rolling. There is a gauge for each 
course, or a set of gauges for each size boiler, and also sets 



SHOP-PR A CTICE. 



313 



for the same size, but with different thickness of shell. The 
plates are marked either with a piece of soapstone or with a 
slate-pencil. Rivet-holes are prick-punched at the centre. 
Shearing. — When the plate is laid out it is taken from 




Fig. 155. 

the bench to the shears and any superfluous stock is cut off. 
A shearing-machine is shown by Fig. 155. The lower knife 
is fixed and the upper knife is moved by an eccentric inside 
the head. The eccentric-shaft is coupled to the gear-shaft 
by a clutch that is controlled by a treadle. The weight of the 
sliding-head is counterbalanced by a weight and lever at the 
top. Lugs are shown on the casting near the knives; when 
the machine is required to do extra-heavy work, wrought-iron 
bolts are put through the lugs and screwed up to strengthen 
the frame. 

The machine is driven by a belt with a fast-and-loose pul- 
ley; the shaft carrying these pulleys has a pinion gearing into 
a large gear to give the necessary power for shearing. A fly- 
wheel steadies the motion of the machine; it must be able to 
supply the power for shearing-plates without a large reduction 
in speed. 



3*4 STEAM-BOILERS. 

Punch. — After the plate is sheared to size it is taken to 
one of the punches and all the rivet-holes are punched. Larger 
openings for man-holes and other fittings are cut out by punch- 
ing overlapping holes, thus leaving a ragged edge which is 
afterwards chipped smooth. The plate is not entirely cut away 
at such large openings, but the piece to be removed is left 
hanging at three or four places until after the plates are rolled 
into cylindrical form. If the pieces were removed, there would 
be less resistance to the rolls at such places and the plates 
would have a conical form instead of a true cylindrical form. 

The punches resemble the shears shown by Fig. 155, with 
a punch and die instead of the knives. Machines are often so 
made that they either punch or shear. 

Planing. — After the plate is sheared and punched the 
edges are planed to a slight angle to give a good calking 
edge. 

The planer shown by Fig. 156 has a long narrow bed on 
which the edge of the plate is laid' and to which it is clamped 
by a follower ; the follower is forced down by screws which 
pass through a beam as shown. The tool-carriage is drawn- 
back and forth by a leading-screw ; the tool is made to cut on 
both strokes, and is fed by hand between the cuts. 

Scarfing. — When the plates are joined by a lap-joint the 
proper corners of each plate are heated in a portable forge 
near the planer, and are drawn down or scarfed so that the 
overlapping plates may come close together and not leave a 
space. 

Plate-rolls. — The plates for forming the cylindrical shell 
are bent to shape cold by running them through bending-rolls 
The horizontal roll represented by Fig. 157 has two parallel 
rolls below that are driven in the same direction by gearing. 
The upper roll is adjusted at each end separately, and some 
care is required or the shell will receive a conical shape instead 
of a true cylindrical shape. The bearing at one end of the 



SHOP-PRACTICE. 



3*5 




316 



STEAM-BOILERS. 




SHOP-PRACTICE. 



3*7 



roll can be swung out, as shown by the figure, to remove the 
plate after it is rolled. 

The rolls may be driven in either direction by crossed and 
open belts. The plate to be rolled has one edge introduced 




Fig. 158. 



between the upper and lower rolls, the upper roll is brought 
down and the rolls are started up. The plate is run through 
nearly to the other edge then the top roll is screwed down 



31$ STEAM-BOILERS. 

farther and the rolls are reversed. Thus the plate is run back 
and forth and the top roll is gradually drawn down till the 
plate acquires the proper form. 

The extreme edges of the plate are not bent in this process; 
they are commonly bent afterwards by hammering them with 
sledges. Some rolls have a special device for bending the 
edges ; it consists of two short overhanging rolls about fifteen 
inches long, one concave and the other convex. The ends of 
the plate are fed through these rolls sideways, and are bent 
before they are introduced into the long rolls. 

Vertical rolls, shown by Fig. 158, are coming into use in 
boiler-shops. They take up less floor-space, and the plate after 
it is rolled up into cylindrical form is easily hoisted off from 
the front roll. For this purpose the front roll is counterbal- 
anced and the top end can be swung out clear from the hous- 
ing. The figure shows the rolls as erected by the builders; 
in the boiler-shop the plate at the lower end of the rolls is 
flush with the floor of the boiler-shop. 

The width of plate that can be rolled by either horizontal 
or vertical rolls depends on the length of the rolls. The 
length of the rolls and the reach of the riveter (to be men- 
tioned later) determine the width of plate that can be handled 
in the shop. 

Assembling and Riveting. — When the plates for a boiler 
have been punched, planed, and rolled they are assembled in 
courses, and bolted together ready for riveting. Formerly 
boilers were commonly punched and riveted ; now it is cus- 
tomary to punch the rivet-holes one eighth of an inch smaller 
than the finished size and then drill to the right size after the 
boiler is assembled. This is more expeditious than drilling 
directly, and as all the metal affected by punching is removed 
it gives as good results. It is the custom in most shops to 
drill the holes out at the riveting-machine immediately before 
the rivets are driven and thus each rivet-hole is sure to be 
true. 



SHOP-PRACTICE. 319 

The shells of heavy marine boilers are drilled after the 
plates are assembled without previous punching. A few holes 
are drilled before the plates are rolled and serve for bolting 
the plates in place when the boiler is assembled. There are 
two forms of machines for drilling marine-boiler shells. In one 
the boiler is placed horizontal on rollers so that it may be 
readily turned, There are two or three upright frames each 
carrying a drill. The frames may be adjusted lengthwise of 
the boiler, and the drills may be set at any height or turned at 
an angle. When a longitudinal seam is drilled the boiler is 
rotated to bring a row of rivets to a drill, and the frame is trav- 
ersed from hole to hole. When a ring-seam is drilled the 
drill is brought to the proper place, and the boiler is rotated so 
as to bring the rivet-holes in succession to the drill. The 
other machine has the boiler placed on one end and the verti- 
cal frames carrying the drills can be rotated into place, and the 
boiler can be turned on a vertical axis. 

If plates are punched and riveted without drilling, the 
holes should be punched from the side of the plate which 
comes in contact with the other plate. The reason for this 
is that the die is always a little larger than the punch and the 
hole is slightly conical, larger at the side where the die holds 
up the plate. If the smaller ends of the holes in two plates 
are brought together, then the rivet fills the hole better and 
draws the plates up more perfectly as the rivet cools. It is 
clear that three or more overlapping plates should always be 
drilled, as punched holes cannot always be brought together in 
a proper manner. This is aside from the desirability of drill- 
ing all rivet-holes. 

Returning now to the assembling of a cylindrical boiler, 
the process is as follows : The back head is put in the rear 
course or ring of the shell, and is bolted with six or eight bolts 
through the punched holes. The head and ring are hoisted 
up to the drill near the riveter, and six or eight holes are 
drilled at about equal distances around the seam holding the 



320 STEAM-BOILERS. 

head into the ring or course, and rivets are driven by the 
machine in these holes. The bolts are now taken from the 
punched holes, and all the remaining holes are drilled and 
riveted, completing the ring-seam through the flange of the 
back head. The reason for driving a few rivets first, at equal 
intervals, is that the errors of spacing, when any exist, are 
distributed, and are removed during the subsequent drilling; 
while such errors might accumulate and give trouble if the 
seam were riveted in succession beginning at one point, 
without first driving a few rivets at intervals. 

After the ring-seam through the flange of the head is 
completed, the longitudinal seam or seams are drilled and 
riveted. Here again a few rivets are driven at intervals 
before the seam is riveted up. A few holes at the ends of. 
the seams are left for convenience in joining onto the next 
course. 

The head and first course are now lowered onto the next 
course, which has been assembled in readiness. A few bolts 
are put through the punched holes, and the two courses are 
hoisted up, drilled and riveted in the way already described 
for the rear course. 

When all the courses are riveted together the front head 
is put in with the flange out so that the rivets in that flange 
can be driven on the machine. The closing seams on a boiler 
which, like the Scotch boiler, has both heads set with the 
flange in, must be riveted by hand. 

Rivets are heated in a small forge near the riveter and 
are passed to a man inside the boiler, who picks them up in 
tongs, thrusts them through the holes from within and guides 
the head of a rivet up to the die which is inside the boiler. 
Sometimes the rivets are thrust through from without, in 
which case the man inside the boiler guides the point to the 
die. On the platform of the machine stand the riveter and 
two or three helpers. They adjust the boiler so that the 
rivet is brought between the dies, and the riveter pulls the 



SHOP-PRACTICE. 



321 



lever which controls the ram, and the outer die is driven 
against the rivet, forming the head and closing up the rivet 
in the joint. 

The holes are drilled about one sixteenth of an inch larger 
than the rivets. The pressure of the dies varies from 20 to 
70 tons, depending on the thickness of the plate ; enough to 
compress the rivet and fill the hole completely. The rivets, 
as they cool, shrink and draw the plates firmly together. 

Riveting-machines. — There are four types of riveting- 
machines used for boiler-work, depending on the method of 
moving the ram or plunger which carries the movable die. 
The motion may be derived from — 

1. A cam and toggle. 

2. A hydraulic cylinder, 

3. A combination of a hydraulic cylinder with a cam and 
toggle. 

4. A steam-cylinder. 

The cam and toggle riveter is now seldom used. In it 
the ram carrying the movable die is driven by a toggle-joint 
that is closed by a cam, which in turn is driven by a belt and 
gearing. The adjustment for different thicknesses of plate is 
made by a wedge behind the ram, which can be set by aid of 
a screw. The pressure on the rivet is controlled by the elas- 
ticity of the frame of the machine and the setting of the 
wedge ; it cannot be regulated satisfactorily. 

The hydraulic riveter, in one form or another, is most com- 
monly used at the present time. With it a definite pressure 
can be applied to each rivet whatever the thickness of plate. 
Fig. 159 represents a hydraulic riveter with a reach of 96 
inches which can apply a pressure of 150 tons. It consists 
essentially of two heavy cast-iron levers or beams, bolted 
together near the middle and at the lower end. One beam 
carries the fixed die at its upper end ; the other carries the 
ram and hydraulic cylinder. The stroke of the ram can be 
adjusted and is controlled by a single lever. The ram moves 






322 



STEAM-BOILERS. 



in straight girders, and may apply an eccentric pressure with- 
out rotating or springing. 

Some hydraulic riveters have a hydraulic closing device 




ric 159. 
for holding the plates together while the rivets are driven. 
Even when furnished it is commonly not used. 

The reach of a riveting-machine is the distance from the 
dies to the bed-plate at the middle of the machine. It limits 
the width of plate that can be riveted by the machine. 

A portable hydraulic riveter is shown by Fig. 160, which 
has a reach of 12 inches and can apply a pressure of 75 tons. 



SHOP-PRACTICE. 



3 2 3 



It can be swung into position by a crane and can be turned to 
any angle by the gear at the trunnion. This type of ma- 
chine is used largely for bridgework; it is sometimes used 
for riveting nozzles, manhole-rings, brackets, and reinforcing- 
plates onto boilers. 

The power for working a hydraulic riveter is derived from 
either a steam-pump or a power-pump. A heavy geared 




Fig. 160. 
power-pump is shown by Fig. 161; it is run continuously 
and delivers water to an accumulator from which water is 
supplied to the hydraulic cylinder which moves the ram. 
The accumulator consists essentially of a loaded piston or 
plunger. Water is pumped into the cylinder of the accu- 



3 2 4 



STEAM-BOILERS. 



mulator, and is drawn out by the hydraulic cylinder as needed. 
When the accumulator reaches the end of its stroke it closes 
a valve on the pipe from the pump so that it receives no 
more water; at the same time it opens a by-pass from the 
delivery to the suction of the pump which continues to run. 
but has at that time very little resistance to overcome. When 




Fig. 161. 

some water has been withdrawn from the accumulator the by- 
pass is closed and the valve on the delivery-pipe is opened. 
When a steam-pump is used there is a device for shutting off 
steam from the pump when the accumulator is near the end of 
its stroke ; and letting it on again when more water is required. 
An accumulator, shown by Fig. 162, is loaded by scrap- 
iron in a plate-iron cylinder. Inside the plate-iron cylinder is 



SHOP-PRACTICE. 



325 



a cast iron cylinder which is closed at the top and which moves 
on a fixed plunger. This plunger passes through a stuffing- 
box and is carried by a cast-iron bed-plate. "When water is 




Fig. 162 



pumped into the cylinder through a passage in the fixed 
plunger, the whole weight of the cylinder, plate-iron casing, 
and scrap-iron load are lifted. The pressure required to do 



326 



STEAM-BOILERS 



this depends on the load ; it is the pressure which is exerted 
on the plunger of the hydraulic cylinder moving the ram. 
The frame of I beams at the sides forms a guide for the 
accumulator-cylinder and its load. 

Another form of accumulator, loaded with heavy cast-iron 
blocks and without any exterior guides, is shown by Fig. 163. 







Fig. 163. 



The Jiydranlic riveter with toggle and cam combines the 
simplicity of the cam-and-toggle machine with the advantage 
of a definite and determinable pressure on the rivet, which is 
the best feature of the hydraulic machine. The toggle bears 
against the ram at the front end, and against the plunger of a 
hydraulic cylinder at the back end. The cylinder is connected 
with an accumulator which is loaded to give the desired pres- 
sure on the rivet. Suppose that pressure to be 30 tons; then 



SHOP-PRA CTICE. 327 

when the cam closes the toggle, the rear end, resting against 
the hydraulic plunger, remains at rest, and the front end 
drives the ram and compresses the rivet till a pressure of 30 
tons is reached. When that pressure is reached the hydraulic 
plunger yields, forces water into the accumulator and raises 
the load on it. When the cam releases the toggle, the hy- 
draulic plunger moves forward and the load on the accumula- 
tor falls and drives water into the cylinder. The stroke of 
the hydraulic plunger may be very short, .as the principal part 
of the stroke of the ram is made before the plunger yields. 
There is no loss of water except by leakage, which may be 
made up from time to time by a hand-pump. This machine 
gives a definite pressure on the rivet whatever the thickness 
of the plate, like the plain hydraulic riveter. It has no pump 
and the accumulator is smaller. If the plunger has a large 
area, the load on the accumulator need not be very great. 

Hand-riveting. — In a modern boiler-shop almost all the 
riveting is done by machine because it is cheaper and, espe- 
cially on heavy work, is more likely to be well done. There 
are, however, a good many rivets on any boiler that must be 
driven by hand. In such case the rivet, which may be heated 
entirely or at the point only, is thrust through the hole from 
within and is held up by a man inside, who has for this pur' 
pose a hammer or weight which weighs about 20 pounds on a 
long handle. He has also an iron hook which he hooks into 
a rivet-hole, and against which he gets a purchase to hold the 
rivet up while it is driven. Two men with hammers that 
weigh about 5 pounds drive the rivet, striking in turn. A few 
heavy blows are struck to close the joint and partially form 
the head, then the head is finished in the shape of a straight- 
sided cone with lighter hammers. If the rivet is long enough 
to form a good head, and if it is driven with care and skill, 
hand-riveting may be equal to machine-riveting. If the heads 
are ill-formed, or if they are too low, the work may be very 
inferior. 

Snap-riveting. — This method of riveting, which is espe- 



328 STEAM-BOILERS. 

cially convenient for driving rivets in contracted spaces, has 
some resemblance to machine-riveting. The rivet is thrust 
through the hole and held up from within the boiler. The 
joint is closed and the head is roughly formed by a few blows 
of a heavy hammer, then a snap or die is held on the rivet 
and driven with sledge-hammers. For large rivets the sec- 
tion of the snap should be a parabola, and the head should be 
relatively small in diameter and high, because this form causes 
the rivet to fill the hole better and makes sounder work. 

Tube-expanders. — The tubes are expanded into the tube- 
sheets to make a steam-tight joint, beginning at the least acces- 
sible end. They are commonly a little too long and are cut 
off at the projecting end by a tube-cutter. The tubes extend 
through the heads a slight amount, and are beaded over, after 
they are expanded, by a special tool. The expanders most 
commonly used are known as the Prosser and the Dudgeon 
expanders. 

The Prosser expander, represented by Fig. 164, is made up 




Fig. 164. 
of a number of steel segments held in place by a spring on a 
cylindrical extension of the segments. The acting part of the 
segments have the form to be given to the tube after it is 
expanded. The inside of the segments forms a straight hol- 
low cone into which a steel taper pin fits. The expander is 
forced into the tube and is expanded by driving in the pin 
with a hammer. This should be done gradually so as not to 
distress the metal of the tube too much, and the expander 
should be frequently slacked back and shifted part way round 
on account ol the spaces between tne segments. 



SHOP-PRACTICE. 



3 2 9 



The Dudgeon expander, Fig. 165, has a set of rolls, three or 
more, in a frame. The rolls are forced out against the sides 
of the tube by driving in a taper pin. The pin and frame are 




Fig. 165. 

rotated as the pin is driven, and the rolls gradually force the 
tube against the tube-plate. 

Fig. 166 shows a self -feeding tube expander of the same type 
as the Dudgeon. 




Fig. 166. 



Although the two expanders accomplish much the same 
result, the action is different. The Prosser causes an abrupt 
stretching of the tube while the Dudgeon rolls the tube out grad- 
ually. One expander seems to be as good as the other. 

The expanded end of the tube conforms to the shape of the 
segments of the Prosser expander or to the shape of the rolls 
used in the Dudgeon. In general, the tube ends expanded by 
the two expanders will appear as in Figs. 167 and 168, which are 
drawn out of proportion to show the difference more clearly. 

An inexperienced person who may be using a tube expander 
for the first time may judge when a tube has been expanded 
sufficiently to be tight by watching the plate around the tube 



33° 



STEAM-BOILERS. 



to see when fine hair-like cracks appear in the scale which covers 
the outside of the plate. 

When these lines show it means that the tube has been made 
to fill the hole and that the hole has begun to be stretched. 

After the tubes are expanded the ends are beaded over by a 
special tool known as a boot-tool. 

Beading adds a little to the holding power of a tube. Tube 
ends which are directly over a furnace, as is the case in vertical 





Fig. 167. 



Fig. 168. 



boilers like the Manning, should always be beaded. This bead- 
ing keeps the end of the tube in such cases from being eaten 
away by the fire. 

A vacuum may possibly be found in a boiler, if it is allowed 
to cool without admitting air. The Prosser method has an 
advantage in such case, when the tubes act as struts between 
the heads. The Dudgeon method will then act by friction 
only. The rollers might be shaped to give an expansion just 
inside the plate, instead of making them straight; there is, 
however, no evidence of trouble from this source in practice. 



SHOP-PRACTICE 



331 



Calking. — The riveted seams of a boiler are made steam 
tight by calking, which consists in driving the lower part of 
the planed edge forcibly against the plate beneath. Fig. 169 
shows the form of calking-tool used in hand-calking, the posi- 




Fig. 169 

Hon in which it is held, and the way the extreme edge of the 
plate is compressed against the plate beneath. The acting sur- 
face of the tool, which is about an incn wide, is ground at an 
angle of somewhat less than 90 , and the edge is rounded 
slightly so that it will not cut the lower plate. The tool is slid 
along the under plate against the edge of the upper plate and 
struck with a hammer. If the tool is ground to a sharp edge 
and used carelessly, a groove may be cut in the under plate 
and serious injury may be done. 

A pneumatic calking-machine or tool is now used for 
doing most of the calking in boiler-shops. In general prin- 
ciple it resembles a rock-drill, and consists of a cylinder in 
vimich works a piston and rod on the end of which is the 
calking-tool. Air is supplied for working the piston, at a 
pressure of 60 or 80 pounds, through a flexible tube. It 
makes about 1500 working- strokes a minute, 3/16 of an inch 
long. The calker, which is about 2^ inches in diameter out- 
side and 15 inches long over all, is held by a workman who 
presses it slowly along the seam to be calked. The edge of 
the tool is well rounded so as not to injure the lower plate. 



332 STEA M-BOILERS. 

Work can be done four times as rapidly with the pneumatic 
calker as by hand. 

Cold-water Test. — After the boiler is calked it is tested 
to about once and a half the working pressure, with cold 
water. During the test the boiler is carefully watched to 
detect any notable change of shape or other sign of faulty 
design or construction, and important leaks are marked ; 
•small leaks are of no consequence, as they will fill up with 
rust. Important leaks must be calked after the pressure is 
relieved ; if necessary, pressure may be applied again to see if 
they are stopped. 

If the boiler is examined by a boiler-inspector, he makes 
his inspection before the boiler is painted, and stamps certain 
letters on the head or over the fire-door to show that the 
boiler has passed inspection. 

Finally the boiler is painted and oiled ready for shipping. 



CHAPTER XL 
BOILER-TESTING. 

The main object of a boiler-test is to determine the 
amount of water evaporated per pound of coal, or, more ex- 
actly, the amount cf heat transferred to the boiler per pound 
of coal burned. For this purpose it is necessary to deter- 
mine : 

i. The number of pounds of water pumped into the boiler 
during the test. 

2. The number of pounds of coal burned, and the weight 
of ashes left. 

3. The temperature of the feed-water when it enters the 
boiler. 

4. The pressure of the steam in the boiler. 

5. The per cent of moisture in the steam discharged from 
the boiler. 

It is desirable to determine the conditions of combustion, 
such as the draught, the weight of air supplied per pound of 
coal, the composition of the products of combustion, and the 
temperature of the escaping flue-gases. It is also desirable to 
have determinations made of the composition of the coal and 
its total heat of combustion, but, as was explained in Chapter 
II, these determinations should usually be intrusted to a 
chemist and to a physicist. 

Water. — The best and most satisfactory way is to weigh 
the feed-water directly, in proper tanks or barrels on scales. 
There should be two barrels or tanks large enough so that the 
iilling, weighing, and emptying may proceed without haste. 

333 



334 STEAM-BOILERS. 

The scales should be adjusted and tested with a standard 
weight and should be known to be correct and sensitive. 
Good commercial platform scales are sufficient for this pur- 
pose. 

The weighing-barrels should be placed high enough to 
discharge into a tank or reservoir from which the feed-water 
is drawn by a pump or injector. This tank should hold more 
than both weighing-barrels, so that when it is about half 
empty an entire barrelful of water may be discharged into it 
without danger of overfilling it and wasting water. The bar- 
rels are emptied through large quick-opening lever-valves; 
this point should receive attention, as any delay caused by 
small valves is very annoying. 

The weighing-barrels are filled either from a water system 
or by a special pump from a well or reservoir, When a direct- 
acting steam-pump is used, a quarter-inch by-pass should be 
carried from the delivery-pipe to the suction-pipe; the pump 
will then run slowly when the valves on the pipes leading to 
the weighing-barrels are shut ; when one of these valves is 
opened the pump starts away promptly, and it slows down 
again when the valve is shut. If a power-pump is used, it 
may be convenient to arrange so that it shall run all the time 
at full power, discharging into the well or reservoir when 
neither barrel is filling. 

Weighing water, though simple enough, requires care and 
intelligence, as any blunder will spoil the test. The observer 
should proceed systematically. He will naturally start with 
both barrels filled, weighed and recorded before the test 
begins. When the level in the feed-tank has fallen so that it 
can receive a barrelful of water he will open the discharge- 
valve from one barrel, which should be marked and designated 
as Barrel No. I. When that barrel is emptied, he will close 
the valve and weigh the barrel ; the weight empty is set down 
and subtracted from the weight full to get the weight dis- 
cha:ged. The record of weights is kept in a table con- 



B OILER- TES TING. 335 

taining columns for the name of the barrel, weights full, 
weights empty, weights discharged, and time at which dis- 
charged. The weight of the barrel empty must be taken 
each time, as the barrel will not drain completely in the time 
that can be allowed. 

Water may now be turned on to fill Barrel No. 1, and 
Barrel No. 2 may be emptied, as occasion demands. Then 
one barrel may be filling when the other is emptying, and the 
work may proceed rapidly but without confusion. The errors 
that a novice is liable to are either to forget to record the 
weight of a barrelful of water, or to empty a barrel that has 
not been weighed. 

It is convenient and almost necessary to have some sort of 
an index or telltale to show the water-weigher where the 
water-level is in the feed-tank. For this purpose we may use 
a float, with a string that runs up over a pulley and is kept 
taut by a small weight moving over a scale, which is placed 
in front of the weighing-barrels. This float is not used to 
determine the level of the water in the feed-tank at the begin- 
ning and end of the test. 

At the beginning of the test the level of the water in the 
feed-tank is marked, and at the end of the test the level is 
brought to the same mark, so that all the water delivered by 
the weighing-barrels is drawn out of the feed-tank by the 
feed-pump. A good way of marking the water-level is to 
fasten to the side of the tank a piece of wire bent into a hook, 
with its point projecting slightly above the water-level. This 
hook will commonly be placed in position before the test 
begins, and the tank will be filled up to the level so marked 
before water is drawn from the feed-tank. 

If water cannot be weighed directly, it may be measured 
in tanks of known capacity which are alternately filled and 
emptied. Or the water may be measured by a good water- 
meter, which must be tested under the conditions of the test 
to determine its error. Care must be taken to keep the meter 



33 6 STEAM-BOILERS. 

free from air or it will record more than the amount of 
water which actually passes. Boiler-tests on steamships can 
scarcely be made without using meters. 

At the time when the test begins, the water-level is noted 
at the water-glass, and at the end of the test the water-level 
is brought to the same place. The best way is to fix a 
wooden scale near the water-glass and record the height of the 
water above an arbitrary point on the scale. Sometimes a 
string is tied around the glass at the water-level when the test 
is started ; in such case the distance of the string from some 
fixed point on the fittings of the water-glass must be recorded, 
so that the string can be replaced if it happens to be moved 
or if the glass tube breaks. If the water is not brought 
exactly to the same level at the end as at the beginning of the 
test, the difference is noted and allowance is made. It has 
already been pointed out that the apparent height of the 
water depends to a certain extent on the rate of vaporization 
and on the rapidity of circulation in the boiler; consequently 
the boiler must be making steam at the same rate at the times 
when the water-level is observed for beginning and ending the 
test. 

All pipes leading water to or from the boiler, except the 
feed-pipe, must be disconnected. Steam may be taken for 
any purpose and through any pipe, so far as the boiler-test is 
concerned. 

Frequently the steam used by an engine is determined by 
weighing the feed-water for a boiler which is used exclusively 
for that engine. If the boiler is fed by an injector, the steam 
for running the injector should be taken from the boiler, for 
it will be condensed by the feed-water and returned to the 
boiler. A very small amount of the heat (less than two per 
cent) in the steam supplied to an injector is used in pumping 
the feed-water; the remainder is used in heating the feed- 
water and is returned to the boiler. The temperature of the 
feed-water must be taken before it goes to the injector. If the 



BOILER-TESTING. 337 

boiler is fed by a direct-acting steam-pump, that pump should 
be run with steam taken from some other source. If that 
cannot be done, then the steam used by the pump must be 
determined and allowed for, unless the exhaust from the 
pump can be turned into and condensed by the water in the 
feed-tank, in which case the pump is in the same condition 
as an injector. The best way of determining the amount of 
steam used by a steam-pump is to condense it in a small sur- 
face condenser, and to collect and weigh the condensed water. 
Or the steam may be run into a barrel filled with cold water, 
which is weighed before and after steam is run in. This 
method requires that the barrel shall be emptied when the 
water begins to vaporize, and filled afresh with cold water. 
Steam used by a calorimeter for determining the amount of 
water in steam must be ascertained also; the methods will be 
given in connection with a description of the instruments. 

Coal and Ash. — The coal required during a boiler-test 
should be brought in as required in barrows; it may be fired 
from the barrow or dumped and fired from the floor. The 
barrow should be weighed full and empty, and the difference 
should be recorded together with the time ; the latter to serve 
as a check on the record and make sure that a barrow-load is 
not neglected. The weight of the barrow is usually the same 
throughout the test. Any coal left unburned is weighed back 

It is essential that the condition of the fire shall be tne 
same at the beginning and at the end of the test. There are 
two methods in vogue for trying to attain this result ; if the 
test is 24 hours long or more, the condition of the fire is esti- 
mated by its appearance; if the test is 10 or 12 hours long, 
the test is started and stopped with the grate empty. These 
are for tests of factory boilers with a combustion of 15 to 20 
pounds of coal per square foot of grate per hour. For tests 
on marine or locomotive boilers, where the rate of combustion 
may be twice or five times as rapid, the duration of a test 
may be correspondingly reduced. 



338 STEAM-BOILERS. 

Coal in solid mass will weigh 70 or 80 pounds to the cubic 
foot; when lying on a grate it will weigh 50 or 60 pounds. 
It is difficult to estimate the thickness of the bed of coal on a 
grate nearer than two inches. But a layer of coal two inches 
thick will weigh 8 or 10 pounds, which is about half the rate 
of combustion for a factory boiler. If a test is only ten hours 
long, the error resulting from a wrong estimate of the thick- 
ness of the fire may readily be five per cent. If the test lasts 
twenty-four hours, the error will probably not be more than 
two per cent, provided a proper method is used. 

If the condition of the fire is estimated at the beginning 
and end of the test, the fire should be cleaned and freed from 
ashes and clinker shortly before the test begins, and should 
then be spread in rather a thin even layer of clean glowing 
coal. Its height above the grate should be estimated with 
reference to some mark in the furnace that can be recognized 
readily. Just as long before the end of the test the fire 
should be cleaned and levelled in the same manner, and the 
thickness should be estimated with reference to the mark 
chosen at the beginning. The fireman is sure to have a clean 
bright fire at the beginning of the test, but he is apt to have 
a fire with much the same appearance that is half clinker at 
the end. The error from estimation may be very serious in 
such case, even though the test is 24 hours long. 

If the test is started and stopped with the grate empty, 
the boiler must be brought into good working condition about 
an hour before the test is to start, with all the brickwork 
thoroughly heated. The fire is allowed to burn low, and the 
steam-pressure is maintained by reducing the draught of 
steam from the boiler. Twenty or thirty minutes before the 
test starts, the fire is drawn or dumped and the grate and ash- 
pit are cleaned out. A new fire is started with wood, and 
coai is thrown on as soon as the wood is well alight. The 
time when coal is thrown on is counted as the beginning of 
the test. If the steam-pressure falls while the fire is drawn, 



BOILER-TESTING. 



339 



the stop-valve may be nearly or quite closed to keep it from 
falling much below the working-pressure. Toward the end of 
the test the fire is allowed to burn low, and at the end of the 
test it is drawn out on the boiler-room floor and quenched with 
as little water as may be, not enough to leave it wet. The 
unburned coal is picked out by hand and weighed back, the 
clinker and ashes are separated and weighed together with the 
clinker withdrawn during the test and the ashes in the ash-pit. 

If any appreciable amount of coal falls through the grate, 
a sample from the ash-pit may be picked over by hand to es- 
timate the proportions of unburned coal in the ash. The coal 
in the ash is allowed for in calculating the per cent of ash in 
the coal, but is not added to the coal weighed back, for there 
is no way of burning coal thus lost through the grate. When 
a test is started with a wood fire, more or less coal is apt to 
fall through the grate in starting. This is drawn from the pit 
and fired over again. 

It is customary to allow the fire to burn low before draw- 
ing the fire at the end of the boiler-test, both because it brings 
the fire more nearly to the condition at the beginning, and 
because it is a hard and unpleasant job to draw a thick fire. 
But the fire should be maintained at its normal condition 
until the end of the test approaches, and should be a good 
fire when drawn. Extraordinary results may be obtained by 
allowing the fire to burn nearly out at. the end of the test, a 
very considerable amount of steam being formed by heat 
given out by the boiler-setting. It is unnecessary to say that 
such results are entirely misleading. 

The wood used for starting the fire is weighed and allowed 
for on the assumption that a pound of wood is equivalent to 
0.4 of a pound of coal. The total weight of wood used is not 
large. 

Temperature of Feed-water. — The temperature of the 
feed-water is taken by a thermometer in a cup filled with oil, 
screwed into the feed-pipe close to the check-valve. If the 



3 4° STEA M- BOILERS. 

temperature varies, it may be read every five minutes: if it 
is found to be steady, less frequent intervals will do. 

Pressure of Steam. — The steam-pressure must be very 
nearly the same at the beginning and end of a test, and 
should remain nearly constant throughout the test. Read- 
ings are commonly taken every fifteen minutes, but the fire- 
man should be required to keep the pressure nearly constant 
at all times. 

The steam-pressure is taken by a spring-gauge like that 
shown by Fig. 108 on page 269. The gauge should be 
compared with a mercury column or a standard gauge both 
before and after the test, and a correction should be applied 
if necessary. If the pipe carrying pressure to the gauge fills 
up with water, allowance for the pressure of that column of 
water must be made. Each foot of water will give a pressure 
of about 0.43 of a pound per square inch. 

The reading of the barometer should be taken two or 
three times during a test. The reading in inches of mercury- 
can be reduced to pounds per square inch by multiplying by 
the weight of a cubic inch of mercury, which is about 0.491 
of a pound. 

Very commonly the pressure of the steam is obtained 
indirectly by aid of a thermometer set in the steam- pipe. 
The absolute pressure corresponding to the temperature is 
then obtained from a table of the properties of saturated 
steam. The thermometer is readily standardized, and is not 
so likely to become unreliable as a steam-gauge. 

Most vertical boilers and some water-tube boilers give 
superheated steam ; in such case there should be both a 
thermometer and a gauge on the steam-pipe, to indicate tem- 
perature and pressure. The excess of the temperature by 
the thermometer above that corresponding to the absolute 
pressure of the steam, as found in a table of properties of 
steam, is the degree of superheating. 

Specific Heat of Superheated Steam. — The mean value 



BOILER-TEST IXC. 



341 



of the specific heat of superheated steam is given in Chapter II. 
The value is commonly represented by c p . The value increases 
with the pressure and at the same pressure decreases as the super- 
heat increases. 

For example, let the pressure by the gauge be 65.3 
pounds, and let the temperature be 350 F. by the thermom- 
eter- The absolute pressure corresponding to 65.3 pounds 
is 80 pounds, at which saturated steam has the temperature 
of 31 1°. 8 F. The superheating is consequently 

350 F. - 3ii°.8 F. = 38°.2 F. 

The heat due to the superheating is 

0.53X38.2 = 20.26. T. U. 

When the steam is superheated, the formula for equiv- 
alent evaporation is changed from the form given on page 
148 to 

c p (t s — t) + r + q — g 

w — — > 

966.3 

in which t s represents the actual temperature of the super- 
heated steam, and t is the temperature corresponding to the 
absolute pressure of the steam determined from the reading 
of the gauge. 

Priming. — A boiler which has sufficient steam-space and 
free water- area will deliver steam which contains less than 
two per cent of moisture. 

Professor Denton * has pointed out that a jet of steam 
blowing into the air from a petcock will give a characteristic 
blue color if there is less than two per cent of water in the 
steam. If there is more than two per cent of moisture, the 
jet will be white. Since steam seldom contains less than 
one per cent of moisture under the usual conditions of 
ordinary practice, it is possible by this method to estimate 
the condition of steam with a probable error of one per cent. 

* Trans. Am. Soc. Mech. Engs., vol. x. p. 349. 



342 



STEAM-BOILERS. 



The most ready way of determining the condition of 
steam is by the aid of a throttling-calorimcter, devised by 
Professor Peabody,* which depends on the fact that the total 
heat of steam increases with the pressure, so that dry steam be- 
comes superheated when the pressure is reduced by throttling. 
If the steam is only slightly primed, superheating will still 
take place, and the amount of priming can be determined 
from the temperature and pressure of the steam after it is 
throttled. If there is much moisture in the steam, it fails to 
superheat. 

A good form of this apparatus is shown by Fig. 170, 
consisting of a reservoir A to which the 
steam to be tested is admitted through 
a -half-inch pipe b with a throttling-valve , . 
near the reservoir. The steam flows 
away through an inch pipe d. At f is 
a gauge for measuring the pressure, and 
at c there is a deep cup for a ther- 
mometer to measure the temperature. 
The boiler-pressure may be taken from 
a gauge on the main steam-pipe near 
the calorimeter. It should not be taken 
from a pipe in which there is a rapid 
flow of steam as in the pipe b, since 
the velocity of the steam will affect 
the gauge-reading, making it less than 
tne real pressure. The reservoir is 
wrapped with hair-felt and lagged with wood to reduce radia- 
tion of heat 

When a test is made the valve on the pipe d is opened 
wide (this valve is frequently omitted), and the valve at b is 
opened wide enough to give a pressure of five to fifteen 
pounds in the reservoir. Readings are then taken of the 




Fig. 170. 



* Trans. Am. Soc. Mech. Engs., vol. x. p. 327. 



bGILEh-TESTIlSlG. 



343 



boiler-gauge, of the gauge at /, and of the thermometer at e. 
It is well to wait about ten minutes after the instrument is 
started before taking readings, so that it may be well heated. 

The method of calculation can be readily understood 
from the following 

Example. — The following are the data of a test made 
with a throttling calorimeter: 

Pressure of the atmosphere 14.8 pounds. 

Pressure by the boiler-gauge 69.8 " 

Pressure by the calorimeter-gauge.. . . 12.0 " 

Temperature in the calorimeter 268°.2 F. 

The absolute pressure in the boiler was 

69.8 -f- 14.8 = 84.6 pounds, 

at which the heat of vaporization is 892.3 B. T. U. and the 
heat of the liquid is 285.9 B. T. U. So that with x part of 
a pound steam (and 1 — x priming) the heat in one pound of 
moist steam was 

892.3* + 285.9, 

in which x was to be determined. The absolute pressure in 
the calorimeter was 

12 -f 14.8 = 26.8 pounds, 

at which the temperature was 243°.9 F M and the total heat 
was 1 1 56.4 B. T. U. The heat due to superheating was 

o. 55 (268 c .2-243 -9) = i3.4B. T.U, 

and the heat in one pound of steam in the calorimeter was 

1156.4 + 13.4 = 1169.8 B. T. U. 

But the process of throttling neither adds nor subtracts heat, 
consequently 

892.3^; + 285.9 = 1 169.8 

or x = 0.991, 



344 STEAM-BOILERS. 

and the priming was 

iod(i — 0.991) — 0.9 per cent. 

The calculation can be conveniently expressed by an equa- 
tion in which r and q are the heat of vaporization at the abso- 
lute boiler-pressure, and \ and t x are the total heat and the 
temperature at the absolute pressure in the calorimeter, all 
taken from a table of proportions of steam; while t s is the 
temperature of the superheated steam in the calorimeter- 
Then 

xr + q=X 1 + Cp (t s -h); 

h+c v (t s —h)-q 

x = — 



It has been found by experiment that no allowance need 
be made for radiation from the calorimeter if made as de- 
scribed, provided that 200 pounds of steam are run through 
it per hour. Now this quantity will flow through an orifice 
one fourth of an inch in diameter under the pressure of 70 
pounds by the gauge, so that if the throttle-valve be replaced 
by such an orifice the question of radiation need not be con- 
sidered. In such case a stop-valve will be placed on the pipe 
to shut off the calorimeter when not in use; it is opened wide 
when a test is made. If an orifice is not provided, the 
throttle-valve may be opened at first a very small amount 
and the temperature in the calorimeter noted after a few min- 
utes; the valve may be opened a trifle more, whereupon the 
temperature will usually rise, showing too little steam used. 
){ the valve is opened little by little till the temperature stops 
rising, it will then be certain that enough steam is used to 
reduce the error from radiation to a very small amount. 

Various modifications of the throttling-calorimeter have 
been proposed, mainly with a view of reducing its size and 
weight. Almost any of them will prove satisfactory in prac- 
tice, but some will be found to be liable to error from radia- 



BOILER-TESTING. 



345 



tion or from the fact that there is not sufficient opportunity 
for the steam to come to rest and properly develop the super- 
heating due to throttling. One great advantage of this 
instrument is that ordinary care with ordinary gauges and 
thermometers gives sufficient accuracy. For example, with 
IOO pounds absolute boiler-pressure and with atmospheric 

pressure in the calorimeter, an error 
of half a degree by the thermometer, 
or half a pound by the boiler-gauge, 
or a third of a pound by the calo- 
rimeter-gauge will each give an error 
of one-tenth of a per cent in the 
priming. 

If steam contains more than three 
per cent of priming, the amount of 
moisture can be determined by a goods 
separator, which will remove nearly 
all the moisture. It remains then 
to measure the steam and water sep- 
arately. The water may be best 
measured in a calibrated vessel or 
receiver, while the steam may be 
condensed and weighed, or may be 
gauged by allowing it to flow through 
an orifice of known size. A form 
of this instrument devised by Professor Carpenter * is shown 
by Fig. 171. 

Steam enters a space at the top which has sides of wire 
gauze and a convex cup at the bottom. The water is 
thrown against the cup and finds its way through the gauze 
into an inside chamber or receiver, and rises in a water-glass 
outside. The receiver is calibrated by trial so that the 
amount of water may be read directly from a graduated scale. 




Fig. 171. 



* Trans. Am. Soc. Mech. Engs.. vol. xvil p. 608. 



346 



STEAM-BOILERS. 



The steam meanwhile passes into the outer chamber which 
surrounds the inner receiver, and escapes from an orifice at 
the bottom. The amount of steam may either be calculated, 
by a method to be explained, from the diameter of the orifice 
and the pressure of the steam, or it may be condensed and 
weighed or measured. The latter is the more accurate way, 
and it has the advantage that then there is no error from 
radiation, for the inner receptacle is well protected by the 
outer chamber, and condensation in the outer chamber is 
collected and weighed with the steam. If the instrument is 
well wrapped and lagged, and if a sufficient quantity of steam 
is used, then the error from radiation can be neglected, just 
as was found to be the case with the throttling-calorimeter.% 
This instrument, for want of a better name, is called a separator 
calorimeter; it is a question whether either it or the throttling- 
calorimeter are properly calorimeters at all, and whether it 
would not be better to call both priming-gauges. 

It is customary to take a sample of steam for the calori- 
meter or priming-gauge through a small pipe leading from 
the main steam-pipe. The best method of securing a sample 
is an open question; indeed it is a question whether we ever 
get a fair sample. There is no question but that the com- 
position of the sample is correctly shown by either of the 
priming-gauges described. It is probable that the best way 
is to take steam through a pipe which reaches at least half- 
way across the main steam-pipe, and which is closed at the 
«nd and drilled full of small holes. It is better to have the 
sampling-pipe enter the steam-pipe at the side or at the top of 
the main, so that any water that may trickle along the bottom 
of the main shall not enter the calorimeter. Again, it is better 
to take a sample from a pipe through which steam flows 
upward. The sampling-pipe should be short and well wrapped 
to avoid radiation. 

If the steam from the boiler can be wasted during the test, 
then the entire steam delivered by the boiler may be passed 



BOILER-TESTING. 347 

through a large priming-gauge, and the difficulty of getting a 
sample may be avoided. 

Flow of Steam.— It has been shown by Rankine * that 
the flow of steam through an orifice into the atmosphere may 
be represented by an empirical equation, 

70' 

in which W is the number of pounds of steam per second, A 
is the area of the orifice in square inches, and p is the absolute 
pressure of the steam. This equation, which has already 
been mentioned in connection with safety-valves, can be 
applied only when the absolute steam-pressure is more than 
double the pressure of the atmosphere; that is, the pressure 
of the steam must be 15 pounds by the gauge, or more. 
Experiments made in the laboratory of the Massachusetts 
Institute of Technology f show that this equation is liable to 
an error of about T 5 o per cent, but this error may be deter- 
mined by direct experiment for a given orifice under various 
pressures, and then a correction can be applied which will 
reduce the error to a fraction of one per cent. 

It appears then that the use of an orifice to determine the 
amount of steam in Professor Carpenter's separator priming- 
gauge is at least questionable unless direct experiments are 
made to determine the correction to be applied. On the 
other hand, the amount of steam used by a throttling prim- 
ing-gauge may be very properly determined by allowing i 4 
to flow through an orifice, since the total amount of steam 
used by the calorimeter is small. 

The same equation may be used for calculating flow of 
steam from one reservoir to another provided that the pres 
sure in the second reservoir is less than half that in the first 



* The Engineer, vol. xxvu. p. 359, 1869. 
+ Trans. Soc. Am. Engs., vol. xi. p. 187. 



348 STEAM-BOILERS. 

reservoir. This allows us to gauge small quantities of steam 
used for any purpose, at a pressure that is less than half the 
boiler-pressure; for example, for running a steam-pump. A 
convenient arrangement for gauging the flow of steam in an 
inch pipe consists of a reservoir three feet long, made up of 
three-inch piping, and fittings divided at the middle by a 
brass plate through which there is an orifice of proper size. 
If the pipe carries steam at ioo pounds absolute, at a velocity 
of ioo feet a second it will deliver 

nd* 3.1416 X ( T V) a 

X 100 = — ^ SL X 100 = 0.5455 

4 4 

cubic feet per second. The density or weight of one cubic 
foot of steam at 100 pounds absolute is 0.2271 pounds. So 
that the pipe will carry 

°-5455 X 0.2271 = 0.124 

of a pound of steam per second. If this weight is put for W 
in Rankine's equation, and if A is replaced by \ nd*, we 
shall have 

7td* X 100 
0.124= , 

* 4 x 70 

or 



_ /0.124 

" V 3-hi 



X 4 X 70 __ l 



6 X 100 3 

of an inch, nearly, for the diameter of the orifice for gauging 
the flow of steam. With an orifice of approximately the 
right size, the flow of steam may be regulated by a valve 
below the gauging device; for example, by the throttle-valve 
of the pump. 

Flue-gases. — At frequent intervals samples of flue-gases 
should be taken from various places, such as back of the 
bridge, from the uptake, and from the chimney. These sam- 



BOILER-TESTING. 



349 



pies are analyzed as soon as may be by Orsat's apparatus, as 
described on page 64. 

Though not commonly done, it would be well if a con- 
tinuous sample could be taken in a reservoir from which 
samples for analysis could be taken at intervals. 

Draught-gauge. — The draught given by a chimney is 
seldom more than an inch or an inch and a half of water. It 
can be measured roughly by a simple U tube filled with water. 
An instrument for accurate determinations of draught should 
be at once simple and certain in its action. 

The draught-gauge shown by Fig. 172, devised by Prof. 




Fig. 172. 



Miller, has been used with satisfaction for this purpose. It 
consists of two pieces of three-inch brass pipe connected by a 
half-inch pipe at the bottom. One of the pipes is closed at 
he top and can be connected to the chimney by a small pipe 
with a valve as shown. The other piece of brass pipe is open 
and has a hook-gauge, reading to 1/1000 of an inch, suspended 
in it. In preparing for a reading, the closed tube or leg is 



35© STEAM-BOILERS. 

shut off from the chimney and opened to the atmosphere; the 
water then stands at the same height aa, a'a\ in both legs. 
The closed leg is now shut off from the air and connection is 
made with the chimney, whereupon the level falls to bb in the 
open leg and rises to b'b' in the closed leg. As the two legs 
have exactly the same internal diameter, the fall ab is half the 
draught, measured in inches of water. The hook-gauge is set 
to the level aa when the closed leg is open to the air, and to 
the level bb when it is connected to the chimney. The 
difference of the readings multiplied by 2 is the draught in 
inches of water. The reading by the hook-gauge can readily 
give an acuracy of i/iooo of an inch, which is sufficient for 
this purpose. 

Pyrometers. — The determination of high temperatures, 
as in flues and chimneys, is difficult and uncertain. Most 
commercial pyrometers, depending on the unequal expansion 
of metals, are unreliable if not misleading; not only is the 
scale of such a pyrometer likely to be incorrect, but the zero 
of the scale is liable to change during use. 

The Chatelier pyrometer has been used with satisfaction 
at the Massachusetts Institute of Technology for measuring 
temperatures in flues and chimneys. It consists essentially 
of a thermoelectric couple made by joining the ends of two 
wires, one of platinum and the other of platinum alloyed with 
ten per cent of rhodium. All but about four inches of the wire 
at the junction is incased in fire-clay inside an iron pipe 
about four feet long. From the wires of the pyrometer con- 
nection is made to a sensitive galvanometer in a separate 
observing-room. The deflection of the galvanometer is indi- 
cated by a ray of light reflected from a mirror on the needle 
and moving over a graduated scale. The scale is set to read 
zero when the junction of the wires is at the temperature of 
the atmosphere. The junction is then immersed successively 
in baths of substances which melt at various high tempera- 
tures, such as sulphur and naphthaline. The readings of the 



BOILER-TESTING. 35 1 

ray of light when the juncture is in such baths fix known 
points on the arbitrary scale from which intermediate tem- 
peratures may be estimated directly. It is convenient to use 
a curve for this purpose with scale-readings for abscissae and 
with corresponding temperatures for ordinates. After the 
scale is determined the pyrometer may be introduced into the 
place or places where temperatures are to be measured, and 
readings are taken from which the temperatures are deter- 
mined by interpolation on the curve just described. 

Air-supply. — The air for a furnace may be made to enter 
through a temporary mouthpiece fitted to the ash-pit doors. 
This mouthpiece may be of galvanized iron, circular in sec- 
tion and about three feet long. Its cross-section should have 
an area equal to that cf the door or doors leading to the ash- 
pit. The velocity of the air passing through the mouthpiece 
can be measured by an anemometer. The area of the mouth- 
piece multiplied by the velocity in feet per second gives the 
volume of air supplied to the ash-pit in cubic feet per second. 
From this may be calculated the volume and weight of air 
supplied to the ash-pit per hour or for the entire test; which 
weight divided by the total coal consumption gives the air 
per pound of coal burned. 

It should be noted that the anemometer is liable to an 
error of from two to five per cent, and further that air enter- 
ing through the fire-doors and elsewhere than through the ash- 
pit is not measured. 

Sample Test. — The test given on page 352, made at the 
Massachusetts Institute of Technology, may serve as an 
example of a convenient arrangement for reporting the data 
and results of a boiler-test. 

The average pressure of the air and of the steam in the 
boiler are liable to vary slightly during the test; the average 
pressures were obtained from readings taken at regular inter- 
vals during the test. The same may be said of the tempera- 
ture of the feed-water. 



352 



STEAM-BOILERS. 



EVAPORATIVE TEST ON BOILER PLANT. 

Date, ^c.30, igoi, 4 P.M., to Jan. 4,1902, 8 A .M. 



DATA. 

Brief description of method of testing : 

The feed-water was weighed and delivered to a barrel connected to the suction of the feed- 
pump. 

Coal was weighed in 300 lb. lots as f red. 

Calorimeter readings were taken every hour. 

Flue-gas sa7iiples every half hour; all other readings quarter hours. 

Fires were cleaned two hours before starting and same time before the ending and twice 
during twenty-four hours. 

Blow-off pipes were blanked. 
Brief description of boilers: 

Boilers No. 4 and No. 5, horizontal multitubular, 16' long. 

Diameter of shed = bo" ; 84 3" tubes lb' long. 

Grates bo%" X bi\Q' {Herringbone grates'). 

Boilers No. b and No. 7 are furnished with Hawley down-draught furnaces ; otherwise 
they are the same as Boilers No. 4 and No. 5. 



Duration of test 

Barometer . . 

Boiler pressure (gauge) 

Temperature of the air 

Temperature of feed water 

Temperature of steam 

Degrees of superheat 

Quality of steam, dry steam unity 

Kind of coal used . 

Moisture in coal, by drying test 

Total water fed to boilers 



20 



^.inches, 



inside. 



br 



■£.c 



F.; outside 



.." C 

..° c 




New River 



T '3 percent 
746,457 pounds. 



Type of Boiler and Number of 
Boiler. 



Horizontal multitubular No. 4. 
" " No. 5. 

No. b. 
" " No. 7. 



Totals . 



Xw 



OS 



/,/bb 



7.166 



25-9 



25-9 



S rt 

"•3 rtrh 

XX2 



42.Q6-7 



42.06-7 



57-45-J 



57-45- 



rt u 

O u 



23,400 



22,780 



20,oqo 



78.Q73 



4,558 Q2.4 49-33-1 84,643 83,544 7,322 76,222 






rtj* 

•c.S 

m — 



23,oq6 



79,829 



78.72b 



1,449 



1,875 



2,055 



2,003 



83 



27, b47 



7 b, 7 23 



Total ash and clinker in per cent, total dry coal 



8.76 



BOILER-TESTING. 
EVAPORATIVE TEST ON BOILER PLANT. 



353 



RESULTS. 
Chemical analysis of coal ^a^ = °-'» C = qo.o, H=o. 5 , S = 0.2, 



O = 1.7, Ash = 7.5. 



Heat of combustion of coal as fired ..... 

Total equivalent evaporation from and at 212 F. 
Equivalent evaporation from and at 212 F. per pound of dry coal . 
Equivalent evaporation from and at 212 F. per pound of combustible 
Equivalent evaporation from and at 212 F. per square foot of heating 

surface per hour. .... 

Coal burned per square foot of grate surface per hour 
Boiler horse-power developed, A. S. M. E. rating 
Maximum assumed possible error of test . 
Air per pound of coal from analysis of flue gases 

Air required per pound of coal from the formula 12 C -f- 36(H ) 

Excess air supplied ..... 
Heat carried off by flue gases per pound of coal 
Heat taken up by water in boiler per pound of coal 
Total heat furnished per pound of coal 
Heat radiated per pound of coal . 
Heat carried off by flue gases 
Thermal efficiency of boiler plant . 
Heat lost by radiation, etc. . 

GAS ANALYSIS : Per cent by volume. 



14,555 B.T.U. 

875>77o pounds. 

10.48 p oun ris, 

H-4Q pounds. 

__LlZ£_pcunds. 
8 - /8 pounds. 
22b 8 



o8 7 per cent. 
3° -7 pounds. 
I0 -° pounds. 



182 per cent. 
2,4 8 5 R T.U. 
lo.ool B.T.U. 
14-555 B.T.U. 
2o69 B.T.U. 
.per cent. 
Tper cent, 
per cent. 



17. 1 



14.2 



CO, 



o a 



CO 



Ash-pit . 
Above grate . 
At bridge wall 



Bet. bridge wall 

and back end 
Back end . 

Uptake 



CO s 



CO 



6.4 



DRAUGHT AND TEMPERATURES. 



Setting. 



Ash-pit 

Above grat3 

At bridge wall 

Between bridge wall and 

back end . 
Back end . 
Uptake . . . 



Inches of 
Water. 



.04 



■ 07 



3QI 



Stack. 



feet above grate. 



Ct (I 



44 « 



Inches of 
Water. 



F. 



Remarks: 

The coal was of poor quality. 
The firing was good. 



Fires were hard to clean, as there were bad clinkers. 



354 STEAM-BOILERS 

Total equivalent evaporation from and at 212° F. : 

(.992;' -\- q) at absolute boiler-pressure is 1178.1 B.T.U. 

(q) at temperature of feed-water ( 75.9 F.) is 44.0 " 

Heat necessary to vaporize a pound of feed-water 

into steam primed .8 per cent is = 1134.1 B.T.U. 

1134.1 X 746457 

w ~ ,* ^3/ . _. 8 S7yo p 0un ds. 

966.3 /D// * 

966.3 is the latent heat of steam at 212 F. 



Equivalent evaporation from and at 21 2 F. per pound of dry coal 

87^770 
'■ — 10.48 pounds. 
83544 4 [ 



Equivalent evaporation from and at 2 1 2° F. per pound of dry 

combustible : 

8 7577° -, 

— -=-?■ — • = 11.49 pounds. 
76222 



Equivalent evaporation from and at 212 F. per square foot of 
heating surf ace per hour: 

8 7577° j 

- 1.72 pounds. 



4558 X 112 



Coal burned per square foot of grate surface per hour „« 

_M 4 i_ = 8.18 pounds. 
92.4 X 112 



BOILER-TESTING 355 

Boiler horse-power developed {A.S.M.E. rating). (See page 148.) 

1134.1 x 746457 = 226>8> 

112 X 333 2 ° 



Maximum assumed possible error of test. — It is assumed that an 
error of one inch may be made in estimating the thickness of each 
fire at the beginning and at the end of the test and that these errors 
are cumulative, thus making the total error two inches over the entire 
grate- For soft coal the weight of a cubic foot is about 48 pounds. 

92.4 X 48 X j2 — 739- 2 pounds error. 
739.2 X 100 



84643 



= 0.87 per cent. 



Thermal efficiency of boiler plant. — This is the ratio of the heat 
taken up by the water in the boilers per pound of coal fired to the 
heat given up by a pound of coal as fired. 

II 34.IX746457XIOO m cent 

14555 X 84643 



Air per pound of coal from analysis of flue- gases. (St" 1 pages 
67-68-69.) 

C0 2 = 6.4X22 = 140.8; T 3 T x 140.8 = 38.4 C 
2 = 12.9 x 16 = 206.9 

CO= 0.1X14= 1.4; |X 1.4= 0.6 C 

348.6 39-oC 

348.6 — 39 = 309.6 2 . 



35& STEAM-BOILERS. 

309.6 



39 

7-94 

.232 



= 7.94 pounds of oxygen per pound of carbon. 
= 34. 2 pounds of air per pound of carbon. 



As the coal is 90 per cent carbon, the air per pound of coal is 
30.8 pounds. 



A ir required per pound of coal from formula : 
i2C+36(H— -J = 12 x .9 + 3 6 (-°°5 + '-g— \ =10.9 pounds. 



Excess of air supplied: 

(30.8 — 10.9)100 
10.9 



182 per cent. 



Heat carried off by the gases per pound of coal. — There were 30.8 
pounds of air and .9 pounds of carbon, making 31.7 pounds of gas for 
each pound of coal burned. 

The proportion of the gases by weight may be figured from the 
flue -gas analysis : 

C0 2 6.4 X22- 140.8 

2 12.9 x 16 = 206.9 

CO 0.1 X 14 = 1.4 

N 2 80.6 x 14 = 1128.4 

100. o 1477.5 ! 

_— — x 31.7 = 3.02, the weight of CO, 
X 31.7 = 4-44> th e weight of O, 



31.7 = 0.03, the weight of CO 



1477-5 

M 
U77-5 

II28 -4 .T. • U C XT 

- X 31.7 = 24.21, the weight of N, 

1477-5 



BOILER-TESTING. 



357 



The temperature of the flue was 391 F., while the air in the boiler- 
room was 6i° F.; a difference of 330 F. 

Multiplying the weights of the gases by their specific heats and by 
the number of degrees increase in temperature. (See pages 55-72.) 

Weight. S P eci f C Temperature fiT 

° Heat. Increase. 

CO2 3-02 .2169 330 216.2 

2 --- 4-44 -2175 330 318.6 

CO 03 .2450 330 2.4 

N 2 24.21 .2438 330 1947-8 

2485.0 

No allowance has been made for the moisture in the coal or for 
the moisture in the air. This moisture might amount to 90 or 95 
heat-units in a total of 2500. 

A much simpler method of finding the heat carried off by the flue- 
gases, although not as accurate as the one given above, is sufficiently 
accurate for most work. 

There are 31.7 pounds of gas per pound of coal; call the average 
specific heat of flue-gas .235. The heat carried away is then 

31. 7X33°X. 235 = 2474, 

which varies from 2485 by but 11 heat-units. 

Heat taken up by the water in the boiler per pound oj coal as fired: 

ii34.iX746457 =lQooiBTIJ> 

84643 

Heat radiated per pound oj coal: 

14555 — 10001 — 2485 = 2069 B.T.U. 

Heat carried off by flue- gases: 

2485X100 

-=17.1 per cent. 

14555 



Heat lost by radiation: 

2069X100 



= 14.2 per cent. 

14555 



358 STEAM-BOILERS. 

Heat Balance. — The heat given up by the coal is accounted 
for as heat put into making steam, as heat carried off by the 
flue-gases, and as heat radiated from the setting to the air. 

The heat taken up in making steam and that carried off by 
the flue-gas may be calculated from the data obtained during the 
test, but the heat lost by radiation can only be found by subtract- 
ing the sum of the preceding from ioo. This should be from 
8 to 15 per cent, depending on how hard the boiler is being forced, 
and on the amount and 'thickness of the brickwork. 

A Scotch boiler will show only 2 to 4 per cent loss by such 
radiation. 

Should the radiation come out negative it shows inaccuracy 
in the test. This inaccuracy may be due to errors in weighing 
coal or to the conditions at the start and at the end not being the 
same. At times, even though an engineer does his best to con- 
duct a test fairly, he may be cheated by the fireman. 

It is not out of place to point out here some of the ways by 
which an unfair result may be obtained by an honest engineer. 

1. By forcing the boiler abnormally for two or three hours 
before the test begins, thus storing up heat in the brickwork 
which is given out later when the boiler is under test. This may 
be obviated by keeping the boiler at its test rating for two hours 
before starting the test. 

2. If a boiler is working hard the water-level is lifted more 
than when the boiler is steaming easily. By crowding the boiler 
for a few minutes just as the test begins and by checking the 
boiler at the end of the test the indication by the glass may be 
made to vary one inch with the same amount of water in the boiler 
at the start and at the finish. 

As the level in the boiler is judged by the height in the glass, 
too much water would be put into the boiler near the end of the 
test when the rate of evaporation decreased. If the boiler is 
kept working at the same rate and at the same pressure through- 
out the test, the error from this source would be avoided. 

3. In many vertical boilers the water connection of the com- 



BOILER-TESTING. 359 

bination carrying the gauge glass comes from the shell just above 
the crown-sheet. 

This makes a column of water outside the boiler perhaps 
10 feet in height. This column is balanced by the water inside 
the boiler. Just before beginning the test the fireman will blow 
out the combination (to satisfy you that it is working freely). 
The piping and glass now fill with hot water, and the level in the 
boiler and the level in the glass are the same. As there is no 
circulation in the pipe leading to the water end of the combina- 
tion, the water gradually cools and a column of cold, or com- 
paratively cold, water is balancing a column of hot water in the 
boiler. 

If the level in the glass is made the same at the end of the 
test as at the beginning, the level in the boiler will be from 6 
to 10 inches higher than at the beginning. By having the com- 
bination blown just before the end of the test this error is avoided. 

4. Sometimes plans to cheat the engineer are deliberately 
made. The engineer may insist that the blow-off pipe and all 
feed-pipes, excepting those from his weighing-tanks, be blanked, 
and yet he may get an impossible evaporation. 

A small pipe 1/4 inch in diameter starting below the water- 
line may lead up inside of the steam-pipe and run perhaps 100 
feet, where it appears on the outside of the pipe as a drip-pipe 
for removing condensation from the pipe. It is evident that if 
this " drip-valve" is manipulated most any evaporation could 
apparently be obtained. 

If an engineer has any doubts about the honesty of the parties 
concerned he may protect himself against any cheating similar 
to that referred to above by cutting the boiler under test from the 
steam-main and by blowing all the steam generated into the air 
through an orifice of known area. 

The weight of steam (figured by Rankine's or Napier's for- 
mula) flowing through the orifice plus the steam used in the 
calorimeter plus the steam used by the feed-pump should equal 
the feed-water weighed. 



CHAPTER XII. 
BOILER DESIGN. 

In order to bring together the principles and methods 
which have been given in the preceding chapters, they will be 
applied to the design of a boiler. Designing of any sort is an 
art that is guided and controlled by practical considerations 
and theoretical principles, and which can be acquired by prac- 
tice only. The design of a boiler, like many other designs, 
is further modified to meet the requirements of government 
boards of inspection, or to conform to the inspection-rules of 
insurance companies. These rules and requirements vary 
from place to place and from time to time; they must be 
known to the designer, but they have no place in a text-book. 
A simple and common type of boiler has been chosen for 
design ; the methods, with proper modification, can be applied 
to other types, and the general principles illustrated are much 
the same for all types. 

Type of Boiler. — The kind of boiler used in a given 
locality depends on custom, on the kind of water used, and on 
the cost and quality of fuel. Deviation from common prac- 
tice should be made only for sufficient reason. Where water 
is bad or where fuel is cheap, the plain cylindrical boiler or a 
flue-boiler will be chosen. With clean, soft water the cylin- 
drical tubular boiler, like that shown by Plate I, has been 
found to be convenient, economical, and cheap. All these 
boilers have external furnaces, so that the shell is in part 
exposed to the fire. Now plates exposed directly to the fire 
should not be more than half an inch thick; 3/8 of an inch is 
preferable. Though thicker plates are sometimes used, this 

3 60 



BOILER DESIGN. 36 1 

consideration limits the size of boilers of this type when high 
pressures are used. The importance of high efficiency for the 
longitudinal riveted joint becomes apparent in this connec- 
tion. 

Internally-fired boilers, like the Lancashire or the Scotch 
marine boiler, are not limited in diameter by this reason. 
The marine boiler sometimes has plates an inch and a quarter 
thick ; the fact that so great a thickness is undesirable some- 
times serves as a check on the size of such boilers. 

General Proportions. — Whatever may be the type of 
boiler chosen, there must be provided — 

1. Sufficient grate-area to burn the fuel required under the 
available draught. 

2. Suitable combustion-space to properly burn the fuel. 

3. Sufficient area or flues or tubes to carry off the products 
of combustion. 

4. Sufficient heating-surface to absorb the heat generated. 

5. Proper water-space to prevent too great a fluctuation 
of the water-level when there is an irregular demand for steam. 

6. Suitable steam-space to prevent too great a fluctuation 
of pressure when steam is taken at intervals, as for the cyl- 
inder of a steam-engine. 

7. Sufficient free-water area for disengagement of steam. 

The last three conditions are not fulfilled by most water- 
tube boilers; some such boilers depend on a separator for 
disengaging steam from water. 

Problem for Design. — Let it be required to determine 
the main dimensions and some of the details of a hori- 
zontal cylindrical tubular boiler to develop 80-horse power 
A. S. M. E. standard (page 148). Let the working-pressure 
be 150 pounds per square inch by the gauge, and the test- 
pressure 225 pounds, or once and a half the working-pressure. 

Assume that anthracite coal will be used, and that it will 
give an equivalent evaporation of 9 pounds of water per 
pound of coal from and at 212 F. Assume further that 12 



362 STEAM-BOILERS. 

pounds of coal will be burned per square foot of grate-surface 
per hour. 

The heating-surface may be about thirty-seven times the 
grate-surface. Tubes 16 feet long will be used, which length 
should not much exceed sixty times the diameter. 

The area through the tubes will be made about 1/7.5 of 
the grate-area. 

Grate - area. — The A. S. M. E. standard requires that 
34.5 pounds of water per hour shall be evaporated from and 
at 212 F. for each horse - power. The total equivalent 
evaporation will consequently be 

80 X 34.5 = 2760 pounds per hour. 

With an equivalent evaporation of 9 pounds of water per 
pound of coal the coal burned will be 

2760 -T- 9 = 307 pounds per hour. 

With a rate of combustion of 12 pounds of coal per square 
foot of grate surface per hour, the grate-area must be 

307 -7- 12 = 25.6 square feet. 

Tubes. — A common rule for finding the diameter of 
tubes is to allow one inch for each four feet of length when 
soft coal is used, and five feet when hard coal is used. A 
tube three inches in diameter will very nearly fulfil this 
condition. 

The table of proportions of flue-tubes in the Appendix, 
gives the area of the internal transverse section of such a tube 
as 6.08 square inches; the external area is 7.07 square inches. 
The internal circumference is 8.74 inches, and the external 
circvmfftrence is 9.42 inches. 






BOILER DESIGN. ' 363 

The aiea through the tubes has been chosen as 1/7.5 of 
the grate-area, equal to 

25.6 X 144 . , 
— = 402 square inches. 

7-5 

Since the area through one tube is 6.08 square inches, 
there will be required 

492 ^6.08= 80.8, 

or, more properly, 81 tubes. It may be found convenient in 
laying out the tube-sheet to use more than this number of 
tubes; a less number is of course improper. 

Steam-space. — A good rule for this type of boiler is to 
allow from 0.8 to 1 cubic foot of steam-space per horse- 
power, which gives from 64 to 80 cubic feet for this boiler. 
We will assume 80 cubic feet. 

For sake of comparison, calculations will be made also by 
rules given on page 132. Thus for certain boilers working at 
moderate pressures it is found that the steam-space may be 
made equal to the volume of steam used by the engine in 20 
seconds. Suppose that this boiler, though designed for 150 
pounds pressure, may run at 70 pounds pressure, and may 
supply an 80 horse-power engine which uses 30 pounds of 
steam per horse-power per hour. 

Now the volume of one pound of steam at 70 pounds by 
the gauge, or 85 pounds absolute, is 5.125 cubic feet. So 
that the engine -will use 

80 X 30 X 5- J 25 = 12,300 

cubic feet of steam in an hour, or 

X 12300 = 68 



3600 



cubic feet in 20 seconds. This is about the lower limit by 
the rule used above. It is clear that the steam-space would 



364 STEAM-BOILERS. 

be very small if determined by this rule for an engine using 
steam at 150 pounds pressure. 

Another rule makes the steam-space from 50 to 140 times 
the volume of the high-pressure cylinder of the engine ; 50 
for very high pressure and high speed, 140 for slow speed 
and low pressure. For medium speeds and pressures 60 to 
90 may be used. 

The boiler under consideration may supply steam to a 
triple-expansion engine which has a high-pressure cylinder 9 
inches in diameter by 30 inches stroke, so that the volume is 
1. 105 cubic feet. According to this the steam-space needed 
is 66 to 99 cubic feet. 

Diameter of Boiler. — For this type of boiler the steam- 
space is commonly made one third and the water-space two 
thirds of the contents of the boiler. To the contents of the 
boiler there must be added the space occupied by the tubes to 
find the volume of the cylindrical shell. Now we have de- 
cided to use 81 tubes 3 inches in diameter and 16 feet long. 
The area of the external transverse section has been found to 
be 7.07 square inches. The space occupied by the tubes is 
consequently 

81 x 7.07 x 16 = 64cubicfeet . 

H4 



To this add steam-space. 



80 



and water- space, 160 



<* 



Making in all, 304 " 

The cylinder is 16 feet long, so that its transverse area is 
304 -^- 16 = 19 square feet; 

which corresponds to a diameter of 59.02 inches, or nearly 60 
inches. This will be taken as the trial diameter; it may re- 
quire change in proportioning other parts of the boiler. 

The method of determining the main dimensions of a 



BOILER DESIGN. 365 

boiler from the steam-space will require modification if it is 
applied to any other type of boiler. Even when applied to 
a given type it leaves much to the judgment of the designer, 
who may find difficulty in using it unless he is accustomed to 
working on that particular type. If the designer has at hand 
the dimension of several boilers of a given type, he may pre- 
fer to select the main dimensions for a new design directly, 
with the reservation that such dimensions may be modified 
as the design proceeds. This is commonly done by the 
designers of marine and locomotive boilers. 

Heating-surface. — The heating-surface of a cylindrical 
tubular boiler consists of all the shell below the supports at 
the side wall, all the inside of the tubes, and part of the rear 
tube-plate. Usually half of the cylindrical part of the shell 
is heating-surface. In the case in hand the heating-surface, 
exclusive of the tube-plate, will amount to 

cu 11 I w S-H^ X 60 X 16 

Shell.... -X — ~ — = 125.7 sq. ft. 

z 1 ±* 

8.74. X 16 
Tubes.... 81 X —^ = 943.9 " " 



Total 1069.6 " " 

The grate-surface is to be 25.6 square feet, so that the 
ratio of grate-surface to heating-surface will be at least as good 
as 

25.6 : 1069.6 :: 1 : 41J. 

The actual ratio will be more favorable as it will appear 
advisable to use more than 8 1 tubes, and the back tube-sheet 
remains to be allowed for. 

Water-level. — It is now necessary to determine the posi- 
tion of the water-level to see if there will be sufficient free- 
water surface and sufficient distance from the water-level to 
the shell above it. 



366 STEAM-BOILERS. 

Since the whole boiler is cylindrical, the area of the head 
of the boiler exposed to steam and to water will have the 
same ratio as that of the steam-space to the water-space. 
Consequently the area of the head above the water-level must 
be one third of the total area of the head less the combined 
areas of the tubes. 

The area of a circle having a diameter of 60 inches is 
2827.4 square inches. The area of 81 tubes each having an 
external cross-section of 7.07 square inches will be 

81 X 7-07 = 572.7 

square inches. The area of the head exposed to steam is 

consequently 

2827.4 — 572.7 ' 
'—± ii — ' = 751.6 

3 

square inches. We need now to know the height of a seg- 
ment of a 60-inch circle, which has the area of 75 1.6 square 
inches. The second problem in the explanation of the use of 
a table of segments (see Appendix; gives for the tabular 
number corresponding to the area 

751-6 

= 0.2088; 



60 X 60 



for which the ratio of the height to the diameter is 0.312. 
The height of the segment is therefore 

0.312 X 60 = 18.7 inches. 

This gives sufficient height above the water, and sufficient 
free-water surface. The water-level will be 

30 - 18.7 = 11. 3 

inches above the centre of the boiler. 

Factor of Safety. — It has been pointed out that the actual 
factor of safety of boiler-shells is usually four or five when the 
boiler is built. The apparent factor of safety for some parts 



BOILER DESIGN. 367 

like stay-bolts may be greater, but such factors are illusory 
because the stays may be subjected to considerable irregular 
stress from unequal expansion. The apparent stress on stay- 
rods and bolts, from steam-pressure only, is frequently limited 
by inspection-rules or by law. 

- The factor of safety of a boiler which has been at work 
for some years is much affected by corrosion, which acts upon 
different parts of the boiler very differently, even when the 
corrosion is uniform. Thus a plate half an inch thick will 
have 7/8 of its original strength after it has lost 1/16 of an 
inch by corrosion. The weakest part of the plate, that is, 
the riveted joint, seldom suffers as much from corrosion as the 
whole plate at a distance from the joint, because the plate is 
protected to some extent by the rivet-heads. Some forms of 
joint have an internal cover-plate, which protects the plate at 
the joint and the joint may be nearly as strong after corrosion 
as before. Very often old weak boilers fail by tearing the 
corroded plate outside the riveted joint. 

Stay-rods and bolts suffer much more from corrosion than 
plates. Thus a rod one inch in diameter has an area of 
0.7854 of a square inch. After corrosion to the extent of 
1/16 of an inch has taken place the diameter is 7/8 of an 
inch and the area is 0.6013, which is 

0.6013 -*- -7854 = 0.766 

ot the original area. Compare this with the plate which 
retains 7/8. or 0.875 °f i ts thickness after the same amount of 
corrosion. Of course a smaller stay will suffer more, and a 
larger one less, in proportion. 

After the sizes of the parts of a boiler are decided upon it 
is well to make calculation to see that a factor of safety of 
four will remain after a reasonable amount of corrosion. Or, 
as in the case of stay-rods, the size may be calculated with a 
proper factor, and then the diameter may be increased to 
allow for corrosion. 



368 STEAM-BOILERS. 

Thickness of Shell. — The final decision of the proper 
thickness of the shell for the boiler under consideration can- 
not be made until the efficiency of the joint is known; but 
the efficiency of any of the complex joints now in vogue can 
be found only when the thickness of the plate is known. It 
is therefore convenient to assume a factor of safety of about six 
and make a preliminary calculation. 

Thus for the boiler in hand we will get for the thickness 
(page 184) 

(= 150x30 

55,000-4-6 ^ 

of an inch. A similar calculation with a factor of five gives 

150X30 

t — = 0.4.Z 

55,000-- 5 

of an inch. The shell will be either 7/16 or 1/2 an inch 
thick. Seven sixteenths will give an apparent factor of 
safety of 

5 5,000 X 7/i6 = m 
150 x 30 

After the allowance for the efficiency of the joint has been 
made this factor will be found to be about 4f , 

Longitudinal Joint. — The shell-plate is made as thin as 
possible because it will be exposed to the fire. Consequently 
the efficiency of the longitudinal riveted joint must be high if 
the real factor of safety is to be satisfactory. The strength 
of triple-riveted joints like that shown on page 214 ranges 
from 85 to 90 per cent. The joint with two cover-plates 
shown by Fig. 173, will be chosen. Following the method 
given on page 214, it appears that this joint may fail in one 
of five ways, for which the resistances are as follows: 

A. Tearing at outer row of rivets: 

Resistance = (P — d)tft. 



BOILER DESIGN. 



3fy 



B. Shearing four rivets in double shear and one in single 
shear: 

gnd 2 



Resistance 



-/.. 



C. Tearing at the middle row of rivets and shearing one rivet: 

nd* 
Resistance = (P— 2d)tf t -\ f s . 



LA _j_ 1 






p (fl 


"*\ 




O 


x. 






O 

c 


) 


c 


) 


O 
O 


O 
O 


c 



) 


c 



]) 


O 
O 


O 
O 


( 


^ 


a f 


> 




O 


\ 


J> 


a % 















Fig. 173. 

D. Crushing four rivets and shearing one : 

Resistance = 4dtf c ~\ f s . 

E. Crushing five rivets : 

Resistance = ^dtf c + dt c f c . 

The diameter of rivet will be found by equating the 
resistances A and C. 

nd 2 

.'. {P-d)tf t = {P-2d)tf t + —f s . 

4 

. jl.*tft 4X tV X 55>ooo . Q 

. \ a = — -j- = = 0.08. 

n fs ^95,000 



370 STEAM-BOILERS. 

The rivet which was used was 13/16 of an inch when driven. 

There are several methods in which we may find the way 
in which the joint will fail, and then find therefrom the effi- 
ciency. One is that shown on page 215 by assuming a pitch 
and calculating the resistance of the joint to failure in each 
of the five several ways. Another method is to equate the 
five several resistances two and two and calculate the pitch ■ 
the least pitch thus found must not be exceeded. Thus 

Equating B and C, 

4 4 

At ft 

8 X 3.1416 x(^|) 
- W 45,000 13 

7 X 55,000 ^ 16 y * 

4X F6 

Equating A and B, 

{p-j)tf<= 9J ffi- 

4* ft 

X 3.i4i6(i|) 
_111_1_W y 45iOOO 13 

- 7 55,000 • 16 y 3 

4X f 6 

Equating A and D, 

(P-d)tf t = A dtf c +—f s . 
4 



BOILER DESIGN. 37 1 



ft 4* ft 



3.1416 x m) 

13 95,000 m6 ; 45,000 £3 _ 

- 4X i~6 X 55~,ooo + 7 _X ^5^o + ^ -7,4 ' 

4X T6 

Equating A and E, 

Jt i ft 
iy 13 Y 95,ooo 13/16 X 3 /8 95.QOO 13 _ 6 

4 16*55,000^ 7/16 x 55, 000^16 '* ' 

Here t c , the thickness of the cover-plate, is taken to be 3/8 
of an inch. 

The greatest allowable pitch at the outer row of rivets is 
evidently 7.4 inches. 

Instead of going to the labor of solving all four of the 
above equations, we may find by some other method how the 
joint is likely to fail, and make up an equation involving 
those resistances only. Thus a rivet in the outer row may 
fail by shearing or by crushing at the cover-plate, which is 
here made thinner than the shell-plate. Equating the re- 
sistances of the two methods, we have 

—■/. = w„ 

4 
or for a cover-plate 3/8 of an inch thick 

a=V<3x 9S ' 000 =i.oi. 

71 45,000 

A rivet 1.01 inch in diameter will consequently be just as 



372 



STEAM-BOILERS. 



likely to fail by crushing as by shearing. But the resistance 
to shearing increases as the square of the diameter, while the 
resistance to crushing increases as the diameter. It is there- 
fore evident that a rivet larger than i.oi of an inch will fail by 
crushing, while a smaller rivet will fail by shearing. 

A similar calculation at the inner row, when the rivet 
bears against a cover-plate both inside and outside, and will 
consequently crush against the shell-plate, gives 

^f s = tdf. 

n 45,000 

Here a rivet larger than 0.6 will crush, and one smaller 
will shear. It is now evident that a 13/16 rivet will shear 
at the outer row and will crush at the inner row. That is, for 
this joint the failure will occur by the method D, but not by 
the methods B or E. Then equating the resistances A and D, 
and solving for P, we get for the pitch at the outer row 7.4 
inches as before. The corresponding pitch at the calking 
edge of the outer cover-plate is 3.7 inches; we will choose for 
that pitch 3f inches, making the pitch at the outer row 7j 
inches. 

The efficiency of the joint is 

P — d 74- — 44 
100- = 100 X ^ ^ = 88.8 per cent. 

P 7i 

In the preceding article the apparent factor of safety 
based on the whole strength of the shell-plate is 5.35. Al- 
lowing for the efficiency of the longitudinal joint, the real 
factor of safety when the boiler is new is 

0.888 X 5.35 =4-75- 



BOILER DESIGN. 373 

With this style of joint the shell-plate is protected from 
corrosion by the inner cover-plate, and the joint will lose 
little if any efficiency from corrosion. If it be assumed that 
the plate loses 1/16 of an inch by corrosion during the life 
of the boiler, then the strength of the plate will be one 
seventh less after corrosion, and the corresponding factor of 
safety will be 

5.35 X f = 4-6, 

which may be considered to be sufficient. 

Ring-seam. — The stress on a transverse section of a 
homogeneous hollow cylinder from internal fluid pressure is 
one half the stress on a longitudinal section. It will in gen- 
eral be found that a single- or a double-riveted ring-seam is 
sufficient for any cylindrical boiler-shell. Marine boilers 
commonly have double-riveted ring-seams ; externally-fired 
horizontal boilers seldom have the shell more than half an 
inch thick, and for that thickness, or less, single-riveted ring- 
seams are used. 

It is found in practice that ring-seams of horizontal ex- 
ternally-fired boilers may have a pitch of about 2 T 3 ^ inches for 
all thicknesses of plate from 1/4 to 1/2 of an inch. The 
diameters of rivets for such seams may be made about the 
size given in the following table : 

Thickness of plate.. ... . J T 5 T f T 7 ¥ \ 

Diameter of rivet f \\ f- \ -J 

The ring-seam in question has a circumference of about 

3.1416 X 60= 188.2 

inches, which will allow us to use 84 rivets with a pitch of 
about 2.24 inches. This joint will fail by shearing the rivets. 
The efficiency of the joint is consequently the ratio of the 
resistance of a single rivet to shearing, to the resistance of 



374 



M -BOILERS. 



a strip of plate as wide as the pitch, 
efficiency is 



Consequently the 



71 d' 



A 



4 Js _ jX 3-i4i6 X (II-) 2 X 45 ,ooo _ 



ptft 



2.24 X xV X 55,000 



= -433, 



which is more than half of the efficiency of the longitudinal 
seam, and will consequently be sufficient. 

Lap. — The lap, or distance from the centre of the rivet to 
the edge of the plate, is usually taken as 1.5 times the diam- 
eter of the rivet used, which makes the distance of the edge 
of the hole from the edge of the plate equal to the diameter 
of the rivet. For the single-riveted ring-seam this makes the 
lap equal to 

1.5 XII- 1.22. 

It is customary to calculate the width of lap required on 
the assumption that the metal between the rivet and the edge 
of the plate may be treated as a beam of uniform depth, fixed 
at the ends and loaded at the centre by the force which would 
be required to shear or crush the rivet, taking, of course, the 
larger. The width of the beam is the thickness of the plate, 
the depth is the distance from the edge of the hole to the 
edge of the plate, and the length is the diameter of the rivet. 

Rivets in single-riveted seams fail by shearing. The load 
is consequently the shearing resistance 



nd' 



/, 



The maximum bending moment for a beam of uniform 
section fixed at the ends and uniformly loaded is equal to 
the load multiplied by one eighth of the span. The moment 
of resistance is equal to 

4 



BOILER DESIGN 



375 



in which /is the cross-breaking strength (about 55,000), /is 
the moment of inertia of the section, and y is the distance of 
the most strained fibre from the neutral axis. Here we have 

M 3 __ h 

\2 2 

representing the distance from the edge of the hole to the 
edge of the plate by h. 

Equating the bending moment to the moment of re- 
sistance, 



4 6 



V 16/ 






v : 



3 x 3-i4i6 X 13 3 45^000 _ 
16 X ^Xi6 s 5 5,ooo °-K 



16 
for the case in hand. The lap is consequently 

0.77+- x iUi.18 

2 16 

inches for the ring-seam, which is somewhat less than that by 
the arbitrary rule that it should be once and a half the diam- 
eter. 

A similar calculation for the cover-plates with the same 
diameter of rivet, but with a plate 3/8 of an inch thick, gives 
for the lap 1.24 or \\ of an inch, while the arbitrary rule gives 
1.03 of an inch. It is probable that the lap may be consider- 
ably smaller than is given by the calculation by the beam 
theory, but for lack of direct experimental knowledge on this 
question it is not wise to make the lap much less than the 
calculation gives; we will consequently use I J- of an inch for 
the lap of the cover-plates. 



376 



STEAM-BOILERS. 



The rivets of the inner rows pass through both cover-plates 
and are in double shear, and consequently fail by crushing 
as is shown on page 372. The load to be used tor calculating 
the lap is therefore the resistance to crushing in front of the 
rivet; that is, we here have for the load tdf c . The equation 
of bending moment and moment of resistance gives 



ttf 



-^dXtdf c =f-^. 



h = <uM = 13/3x95,000 = 6m 

V 4/ i6y 4 X 45>o°o 



The lap is consequently 



0.926 + ^ X y 6 = I.27, 



or a little more than ij. The lap used is if of an inch. 

Tube-sheet. — The next step in the design is to lay out 
the tube-sheet on the drawing-board. If possible, the tubes 
should be arranged in horizontal and vertical rows as shown 
on Plate I. The distance between the tubes should not be 
less than three fourths of one inch ; one inch is better. On 
Plate I the horizontal rows are spaced one inch apart, while 
the vertical rows are only three fourths of an inch apart ; wider 
spacing for horizontal rows is more favorable for the free cir- 
culation of water and the disengagement of steam. The cir- 
culation is improved by having a space in the middle as shown 
on Plate I 

If a very large number of tubes are required for a given 
boiler, they may be arranged in vertical rows and in rows at 
30 with the horizon, as on Plate II. This arrangement is 
commonly used for locomotive boilers, but is not favored for 
stationary boilers. 

The common range of fluctuation allowed for the water- 



BOILER DESIGN. 377 

line with this type of boilers is six inches, three above and 
three below the mean water-level. The tops of the tubes are 
set about three inches below low water-level. 

The rubes should nowhere be nearer than three inches 
from the shell, and the bottom row should be from four to six 
inches from the bottom of the boiler. 

The hand-hole near the bottom of the head should be 
placed as low as possible; the flat surface for the gasket should 
be at least 3/4 of an inch wide. No tube should be nearer 
than an inch from its edge. 

The tube plar.e is usually from 1/16 to 1 8 of an inch 
thicker than the shell -plating. The internal radius of the 
flange should not be less than half an inch. For plates half 
an inch thick or less the outside radius is commonly made one 
inch. 

In applying these principles to the tube-sheet for a boiler 
6c inches in diameter, as shown on Plate I, it appears that 84 
tubes may be used, spaced four inches horizontally and 3J 
vertically and with a space at the middle for circulation, pro- 
vided that the top of the upper row of tubes is 6J inches 
above the centre-line of the boiler. This brings the water- 
level 

6i+6= i2i 

inches above the middle of- the boiler, instead of 11. 3 as cal- 
culated on page 329; that is, the water-level is raised 1.2 of 
an inch or 1/10 of a foot. At 12 inches above the middle, 
the boiler is about 4^ feet wide ; the layer of water added has 
consequently a volume of 

1/10 X 4-5 X 16 = 7.2 

cubic feet. The effect is to reduce the steam-space from 80 
cubic feet (see page 363) to 72.8 cubic feet. But the rule 
used gave from 64 to 80 cubic feet, so that 72.8 cubic feet is 
a fair allowance. If the tubes were spaced nearer together 
in the horizontal rows and the space for circulation were 



378 



STEAM-BOILERS. 



omitted, the required number of tubes could be easily provided for 
without raising the water-level. If in any case a satisfactory ar- 
rangement of tubes cannot be made with the diameter assumed 




from preliminary calculations of steam- and water-space, or from 
some other method, then a larger diameter must be used c 

If a manhole is put in the front head the tube-sheet is as 
shown in Fig. 174. There are now 74 tubes instead of 84, and 



BOILER DESIGN. 379 

the heating-surface is reduced by 116.5 square feet, leaving a 
total of 978.8 square feet, or about 12.5 square feet to a horse- 
power. The head under the tubes is stayed by angle irons tied 
to the head by two through rods. This staying is figured in the 
same manner as the channel-bars, which are considered later in 
this chapter. 

Area of Uptake. — The area of the uptake, like the total 
area through the tubes, is made from 1/7 to 1/8 of the grate 
area. On page 326 the area through the tubes was found to 
be 492 square inches. The uptake may be made 12 inches 
deep, measured from front to rear. It will then be 

492 -^ 12 = 41 

inches wide, measured transversely. The opening through 
the top of the projecting shell at the front end will be made 
12 inches deep, as shown on Plate I, and must be cut down 
till it is 41 inches wide. The projecting end of the shell is 
made long enough so that a space of about one inch is left 
between the uptake and the calking edge of the front tube- 
sheet. 

Length of Sections. — The length of the rings or sections 
of the cylindrical shell is limited by the reach of the riveting- 
machine and by the width of plate obtainable. The sec- 
tions are often made the same length, though there is no other 
reason for this than the convenience in ordering material. 
The two rear sections on Plate I are each made 68 inches from 
centre to centre of riveted joints, or, allowing ij of an inch 
for lap at each end, the plates when finished are 70^ inches 
wide The front section is 

14 + 54f + ii; = 6gi 

inches wide. In this case the plates could all be ordered 
about 72 inches wide. 

The front course which comes over the fire is an outside 
course, so that the flames may not strike directly against the 



380 STEAM-BOILERS. 

edge of the plate at the ring-seam. The length of the grate 
is commonly about one third of the length of the boiler, 
which brings the first ring-seam over the bridge, where the fire 
is the hottest. It is well to avoid this by making the front 
section shorter, and the other sections longer. 

Manholes, Hand-holes, and Nozzles. — These fittings 
should be strong enough and stiff enough to carry the stresses 
which come from the direct steam-pressure and from the ten- 
sion in the pieces to which they are fastened ; for example, 
the manhole-ring must be able to take the place of the piece 
of plate cut away at the hole. 

All these fittings can now be bought in the form of steel 
forgings, made by a hydraulic flanging or forging machine. 
Gun-iron and cast steel are, however, much used. 

The determination of stresses in a manhole-ring, even if 
approximate methods are used, is both difficult and uncertain, 
and will not be considered here. Forms and dimensions that 
have been used in good practice may be taken for a guide in 
designing. A rule used by boiler-makers for forged rings, 
which, like that shown on Plate I, lie close to the shell-plate, 
is to make the section of the ring, exclusive of the lip, equal 
at least to the section of the plate cut away. The aid given 
by the lip against which the cover bears is considered to 
offset eccentric loading, etc. The ring of a steam-nozzle may 
be treated in the same way, though it is more efficiently aided 
by the cylindrical portion. Gun-iron manhole-rings should 
be 1^ of an inch thick, and nozzles may be \\ of an inch thick. 

An approximate calculation of the stress in the manhole- 
cover may be made by treating it as a beam supported at the 
ends and loaded by the steam-pressure and by the pull of the 
bolt at the middle; this last must be assumed, as it cannot be 
known. The calculated stress will be in excess of the actual 
stress, since the plate is supported all around. The handhole- 
plate may be treated in a similar way. Handhole-covers are 
frequently drawn up by a taper key instead of a bolt and nut, 



BOILER DESIGN. 38 1 

because the nut is exposed to the fire, and often cannot be 
removed with a wrench, after it has been in place some time. 

The bearing-surfaces of the manhole-cover and the lip 
against which it bears should be machined to make them 
true and smooth, though this is not always done. The hand- 
hole-cover may be finished, but it bears directly against the 
plate, which of course is not finished. In any case the joint 
is made tight by a gasket which may be 3/4 of an inch wide 
for the hand-hole and from that width to an inch for the man- 
hole. 

Staying'. — As is pointed out on page 238, the calculation 
of stresses in a flat plate supported at intervals can be 
determined only by the application of the theory of elasticity; 
and the only determinate case is that in which the supported 
points are in equidistant rectangular rows, dividing the sur- 
face into squares. This case applies directly to the staying 
of the fire-box of a locomotive by stay-bolts. Whatever 
system of arranging the supported points is finally chosen, it 
is convenient to make a calculation for the determinate case, 
with the points in equidistant rows, in order to get a standard 
with which the chosen system may be compared. 

The equation for finding the stress in a flat plate supported 
at points in equidistant rectangular rows is 

„ 2 a 2 

in which a is the distance of points in a row, t is the thickness 
of the plate, and p is the steam-pressure in pounds per square 
inch. In the design in hand t = g/16 of an inch and/ = 
150 pounds. Assuming 

/=tVX 55,ooo= 5500, 
and solving for a> we have 



faf? / 9X 5500 X 9X9 „ . . , 

== V2"7 = V2Xi50Xi6xi6 = ^+ inches « 



3^2 STEAM-BOILERS. 

If the distance between supported points is made less than 
7 inches, whatever the system of arrangement may be, we 
may be confident that the stresses will not exceed 5500 
pounds; in this case stresses in the plate are due only to the 
pressure on the plate, since the shell of the boiler is self-sup- 
porting. 

In the several ways of staying the flat ends of boilers 
shown on pages 155 to 159 the plate is riveted to channel- 
bars, angle-irons, or crowfeet, which in turn are supported by 
stay-rods. The rivets are in direct tension, and are subject to 
initial stresses due to the contraction when they cool; it is 
customary to limit the apparent working stress to 6000 
pounds. Rivets less than 3/4 of an inch are seldom used, 
since in practice they are found to be too much affected by 
initial stress due to cooling. Large rivets are also considered 
to be undesirable. We will choose here 13/16 for the rivets. 

If each rivet sustains the pressure on a square a inches 
wide, then the stress per square inch on the rivet will be 

~rfs= 150 X a\ 
4 

in which d is the diameter and f s is the tensional stress. 
Assuming f s = 6000 and d= 13/16, and solving for a lt we 
have 



H 



n x 13 X 13 X 6000 . . 

J / r = 4-55 inches. 

150 X 16 X 16 



This gives for the limiting distance of rivets 4.55 inches. 
Of course a less distance may be used if convenient. 

In some cases the pitch of the rivets may be controlled by 
the system of staying. For example, the rods used with 
crowfeet are seldom more than ij of an inch in diameter, 
because larger rods may bring too large a local stress where 
they are riveted to the cylindrical shell. Rods one inch or 
an inch and an eighth are frequently used. A double crow- 



BOILER DESIGN. 



383 



foot has four rivets, each of which will carry one fourth of the 
load on the stay-rod. A stay-rod ij inches in diameter, 
and limited to a stress of 7500 pounds, may carry a pull in 
the direction of its length ol 



*(ii)' 



7500 X = 9204 pounds. 

If the rod makes an angle of 20 with the shell-plate, the pull 
which it will exert perpendicular to the head will be 

9204 cos 20 == 9204 X 0.93969 = 8649 

pounds, so that each rivet will carry about 2162 pounds. If 
each rivet supports a square having the side a 2 exposed to the 
pressure of steam at 150 pounds, then 

2162 = 150 X a 2 % 



or 



/2162 . 

\ / = 3.8 inches. 

V 150 ^ 



Laying cut £tays. — Having selected the form of staying 
to be used, the plan must be laid out on the drawing-board, 
giving proper attention to practical considerations, such as 
the way in which the stays are to be inserted, and taking care 
that accessibility is not too much interfered with. Fig. 140 
repeats the upper part of the head of the boiler shown by 
Plate I, with certain additional dotted lines, which will be 
referred to in the explanation of calculations. The area to 
be stayed is considered to be limited by the upper row of 
tubes, and by a dotted line drawn ij of an inch from the 
inside of the shell. This line is drawn at the right only; it is 
very nearly the place where the rounded corner of the flange 
joins the flat surface of the head. The distance of the lowest 
row of rivets from the top row of tubes, and of the outer row. 
of rivets from the dotted line, may be as great as their maxi- 
mum distance from each other. Rivets should not be placed 
nearer than 3 inches from the tubes, lest the expansion of the 



384 STEAM-BOILERS. 

tubes should start leaks. Rivets may be placed near the 
dotted line, if that is convenient. For example, the outer- 
most row of rivets in crowfoot staying (Fig. 57, page 157) 
may be at a distance <z 3 from the dotted line; for 1^ inch stay- 
rods # 2 = 3.8 inches. 

The method of staying selected consists of channel-bars 
riveted to the head and supported by through-stays; the 
upper channel-bar is assisted by an angle-iron. The channel- 
bars selected are six inches wide, and the horizontal rows of 
rivets in each bar are 2>\ inches apart, which brings them as 
near the flanges of the bar as they can be driven. The mid- 
dle of the lower channel-bar is 5f inches above the top of the 
tubes, so that the lowest row of rivets is 

5*-iX 3i = 4 

inches above the top row of tubes. But the plate cannot be 
properly considered to be rigidly supported at a line drawn 
through the tops of the tubes; we will assume the line of 
support to be a fourth of the diameter lower down. This 
makes a space of 4| inches, instead of the 4.55 inches calcu- 
lated for 13/16 rivets. The excess may be considered to be 
offset by the fact that the other row of rivets in the channel- 
bar is only 3J inches distant. 

The upper channel-bar is placed 8 inches above the lower 
one, so that the stay-rods are 

30-(6i+5l+8) = 9 £ 

inches below the shell. If these upper rods are much less 
than 10 inches from the shell access to the boiler will be diffi- 
cult. The space immediately above the upper channel-bar is 
stayed by aid of an angle-iron which is riveted to the channel- 
bar. 

The distance of the lower row of rivets in the upper chan- 
nel-bar, above the upper row in the lower bar, is 

8 - 3h = 4f 



BOILER DESIGN. 385 

inches — the same as the distance assigned to the lowest row 
of rivets above the assumed line of support at the top row of 
tubes. The top row of rivets in the angle-iron is only a 
little more than four inches below the dotted boundary-line. 

Lower Stay-rods. — In order to determine the load carried 
by the lower stay-rods, we will assume that half the load on 
the plate between the lowest row of rivets and the top row of 
tubes is carried by the rivets, and that the load on the plate 
between the channel-bars is divided equally between them. 
Now we have assumed that the line of support at the tubes is 
a quarter of their diameter below their tops, and have found 
this line to be 4J inches below the loAvest row of rivets. Half 
of 4! is 2-f. Again, tiie distance between the top row of rivets 
in the lower channel-bar and the bottom row in the upper 
bar is 4f inches, of which half is 2-f. The distance apart of 
the two rows of rivets in the channel-bar is 3J- inches. The 
total width of plate supported by the channel-bar may there- 
fore be considered to be 

2 f + 3i + 2| = 8 inches. 

The length of the lower channel-bar at the middle is 52 
inches, as measured on Fig. 142 ; but it is convenient to space 
the rods 13^ inches apart, and to consider the bar to have four 
equal spaces, which leads to an assumed length of 54 inches. 

The load on the lower channel-bar is considered to be 

150 X 8 X 54 = 64,800 pounds. 

We will treat the channel-bar as a continuous girder with 
four equal spaces and five points of support, of which three 
are at the stay-rods and two are at the shell of the boiler. 
By the theory of continuous girders a uniform load on the 
channel-bar would be distributed among the five points of 
supports as follows: At each point of support at the shell 
11/112, at each outer stay-rod 32/1 12, at the middle stay-rod 
26/112. This would bring on each of the outer stay-rods 
ffa X 64,800 = 18,514 pounds. 



SS6 S TEA M-B OILERS. 

Now the load is not uniformly distributed, but is carried in 
part by the rivets and in part by the nuts and thick washers 
on the stay-rods; but the actual distribution will bring a less 
load on the two outer stays, so that the assumption of the 
load just found is on the side of safety, and it is conveniently 
calculated. 

If we assume 9000 pounds for the working-stress in the 
stay-rods, we may calculate the diameter by the equation 

• n ^ __ l8 '5 10 

4 9000 

which 2"ives for the diameter something less than if of an 
inch. For simplicity all five stay-rods will be the same size, 
namely, if of an inch — that required for the two upper stay- 
rods. This is the diameter of the body of the rod; the ends 
are enlarged to 2\ inches where the thread is cut for the nut. 

Lower Channel-bar. — The determination of the actual 
stresses in the channel-bar, allowing for the effect of the nuts 
and thick washers on the stay-rods, is very uncertain. On the 
other hand, the application of the theory of continuous girders 
with a uniform load may not give us a stress as large as the 
actual maximum stress. We will therefore use an approxi- 
mate method, which will give a stress at least as great as the 
greatest stress in the bar. 

For this purpose we will assume that a piece of the 
channel-bar cut by the lines ab and cd (Fig. 175) may be 
treated as a simple beam. These lines ab and cd are drawn 
at one fourth of the diameter of the thick washers from the 
centre of the rod, or at 

i-X 5i= if 

of an inch. We will further assume that the load on the pair 
of. rivets A and B is due to the pressure of the steam on the 
area efgh, bounded by lines drawn half-way between them 
and the nearest point of support. Thus eg is half-way 
between the rivets and the line ab, gh is half-way between the 



BOILER DESIGN. 



387 




3 88 S TEA M-B OILERS. 

rivets and the line of support at the upper row of tubes, ef 
is half-way between the channel-bars, and/// is half-way to 
the next pair of rivets. The rivets are 4| inches from the 
nearest stay-rod, and are 

4f - if = 3t 

inches from the line ab\ half of this is i^-J- of an inch. The 
two pairs of rivets are 

(i3i- 2 X 4f) = 4 
inches apart; half of this is 2 inches. The area of efgh is 

(m + 2)x & = 2 9 i 

square inches; and the steam-pressure on that area is 

29J X 150 = 4425 pounds. 

This is the load due to each pair of rivets between a pair 
of stay-rods; and since the rivets are symmetrically placed, 
this is also the supporting force at each end of the beam. 
Between the two pairs of rivets the beam is subjected to a 
uniform bending moment, equal to the load on a pair of rivets 
multiplied by their distance from the end of the beam; that 
is, the bending moment is 

4425 X 3t= 14934. 
The theory of beams gives 

y 

in which M is the bending moment, / is the moment of inertia 
of the section of the beam, y is the distance of the most 
strained fibre from the neutral axis, and / is the stress at that 
fibre. For rolled-steel channel-bars we may use, for/, 16,000 
pounds, so that with the given value of #we have 

16,000/ / 

14,934 = — , or - = 0.933. 



BOILER DESIGN. 389 

Now /and y depend on the form and size of the section 
of the beam, and, conversely, the size and form of beam 
required may be determined from them. But as the upper 
channel-bar is exposed to a greater bending moment and con- 
sequently must have a larger section than is required for the 
lower bar, we will defer the discussion of this matter, because 
it is convenient to make the bars of the same size. 

Upper Stay-rods. — The flat surface of the boiler-head 
above the lower channel-bar is supported by the upper 
channel-bar aided by the angle-iron which is firmly riveted to 
it, and which will be assumed to act with and form a part of 
the channel-bar. 

Following our general convention that the pressure on a 
portion of the head between two lines of support is divided 
equally between them, we will assume that the load on the 
upper channel-bar is due to the steam-pressure on an area 
bounded at the bottom by a line half-way between the upper 
and lower channel-bars, and at the top by an arc 3J inches 
inside the boiler-shell. On Fig. 175 half of this area is rep- 
resented by jkl\ the arc jk being about half-way between the 
root of the flange, shown by the outer dotted boundary line, 
and the adjacent rivets. In place of the areay'/fc/ we will take 
the rectangular area l?nno, bounded at the end by a line at the 
middle of the end of the channel-bar, and at the top by a line 
mn so chosen as to make the rectangular area larger than the 
area it replaces. The width of this area, Im, is 9^ inches, so 
that the load per inch of length is 

91- X 150= I387-5 pounds. 

The upper channel-bar may be assimilated to a continuous 
girder with three unequal spans; the middle span between 
the stay-rods is i$i inches, and the end spans between the 
stay-rods and the roots of the flange of the head are each 
n£ inches. This makes the end spans nearly 3/4 of the 
middle span. Now, a continuous girder uniformly loaded 



39° 



S TEA M- BOILERS. 



with w pounds per inch of length, which has a middle span / 
inches long, and two end spans f / inches long, will have for 
the end-supporting forces fff^/, and for the middle support- 
ing forces f|-Jte//. The end supporting forces are provided 
by the shell, which is abundantly able to carry them. The 
stay-rods, which furnish the middle-supporting forces, must 
each carry 

ftt X I5i X 1387.5 = 21,083 pounds. 

Assuming a working-stress of 9000 pounds per square inch 
for the stay, the area of the section for a stay is 

21,083 ■*- 9000 = 2.34 

square inches. The corresponding diameter is not quite i|£ 
of an inch. As rods of this size are not regularly carried in 
stock, we will take the next larger regular size, namely, if 
of an inch. This is the size mentioned in connection with the 
discussion of the lower stay-rods. 

Upper Channel-bar. — The calculation of the stress in the 
upper channel-bar will be made by an extension of the same 
approximate method used with the lower channel-bar. Since 
the middle span is wider than the end spans, it will be suffi- 
cient to make a calculation for it only. The calculation is 
made as for a simple beam supported at the ends, the points 
of support being at one fourth of the diameter of the thick 
washer from the middle stay-rod, that is, at the distance of 
if of an inch from the stay-rod. The distance between the 
upper stay-rods is 15J- inches, so that the span of the beam is 

15^ — 2 X if == 12} inches. 

The beam is assumed to be loaded with concentrated loads 
applied at the rivets C, D, E, F, G, and H (Fig. 175); the 
load on the rivet / is assumed to be carried by the stay-rod 
directly, and is not included in this calculation. The pair of 



BOILER DESIGN. 391 

rivets D and E, and the several rivets C, G y and H y are 
assumed to carry the load due to the pressure on the areas 
marked off by the dotted lines on Fig. 140, each line being 
drawn half-way between adjacent supporting points, except 
that the arc at the top is drawn 3J inches from the shell, as 
already said. The calculation of the loads on these rivets, of 
the supporting forces, and of the bending moments is simple 
and direct, but is tedious when stated in detail. We will 
therefore be contented to say that the bending moment at 
the middle of the beam is 37,390. Taking, as with the lower 
channel-bar, a working-stress of 16,000 pounds, we have 

16,000/ / 

37,390 = , or - =2.17. 

The makers of steel beams, channel-bars, and angle-irons 
publish handbooks which give the sizes and properties of the 
standard forms, including the moment of inertia / and the 

ratio -, which is called the moment of resistance. From such 

y 

a handbook it appears that the moment of resistance of the 
channel-bar 6" X 2 J" X J" is 1.08, and that the moment 
of resistance of the 3J" X 3" angle-iron is 1.55; the sum 
2.63 is larger than the required moment of resistance given 
above. These forms are consequently used as shown on 
Plate I. 

Brackets. — The boiler shown on Plate I is supported on 
four cast-iron brackets, each of which is 10 inches wide in the 
direction of the length of the boiler, and 15^ inches long 
measured circumferentialiy. Each bracket is riveted to the 
shell by nine rivets 15/16 of an inch in diameter. Boilers 
over 16 feet long commonly have six brackets. The brackets 
are made wide and long in order that the local strains due to 
carrying the weight of the boiler may not be excessive. The 
rivets are larger than are used about the boiler, as the pitch is 
not restricted as in a calked seam. 



392 



STEAM-BOtLERS- 



The brackets are set above the middle line of the boiler 
so that the flanges may be protected by brickwork. In the 
case in hand they are 3^ inches above the middle; as much 
as 4^ inches is commonly used. 

The brackets are arranged so that the weight of the boiler 
and accessories is equally divided among them, and so that 
there is as little bending-moment as possible on the shell of 
the boiler. When four brackets are used they may be some- 
what less than a fourth of the length of a tube, from the tube- 
plates. 

The load on the brackets may be estimated by calculating 
the weight of the boiler when entirely full of water, and add- 
ing the weight of all parts that are supported by the boiler, 
such as pipes, valves, and brickwork or covering, that may 
rest on the boiler. One fourth of this load is assigned to each 
bracket. This load on a bracket should be uniformly dis- 
tributed over the bearing-surface of the flange, which is com- 
monly 8 or 9 inches wide. But to guard against the effect of 
unequal bearing, it is well to assume the bracket to bear near 
the outer edge — say two inches from the edge. Such an 
assumption will bring the bearing-force on a bracket on 
Plate I, 10 inches from the shell. This bearing-force tends 
to rotate the bracket about its upper edge, and this tendency 
is resisted by the rivets under the flange, which must be large 
enough to resist the resulting pull on them. The other rivets 
are added to give sufficient resistance to shearing all the 
rivets. There are seldom less than nine rivets in a bracket, 
all as large as those below the flange, even though fewer would 
suffice. The bracket is usually made of cast iron, and the 
dimensions are commonly controlled as much by the condi- 
tions required for a sound casting as by calculations for 
strength. The strength may be calculated, treating it as a 
cantilever, allowing for the web connecting the flange to the 
body of the casting. 

Specifications and Contract — The engineer intrusted 



BOILER DESIGN. 



193 



with the design of a boiler prepares a set of working drawings 
and a set of specifications which give all necessary instructions 
concerning the material to be used and the methods of con- 
struction to be followed. The drawings and specifications 
form a part of the contract with the boiler-maker. 

Boiler-makers commonly design standard forms of boilers, 
and in answer to inquiry will furnish a statement or set of 
specifications for a desired boiler in form of a letter, which 
letter forms the contract for the boiler. On the next page is 
given the contract and specifications for the boiler shown on 
Plate I. 



394 STEAM-BOILER. 



RON WORKS CO. 



Boston, Mass., Feb. i, 1807. 



Gentlemen : 



Your letter of received. We will build 

One (/) Horizontal Tubular Boiler. One Boiler, viz., Sixty (bo) inches diameter by 
seventeen 2/12 (/7i 2 z) feet iong. Containing 84 Tubes 3 inches diameter, by sixteen (rb) feet 
long. Shell of Boiler of O. H. Fire-box Steel, y/ib" thick, not less than 53,000 ~or over bo,ooo 
lbs. Tensile Strength. Not less than 50% reduction of area, and 25% elongation in 8". 

Heads of Boiler of O.H. Flange Steel q/ib" thick. Longitudinal Seams Butt Jointed, 
with double covering-plates, Triple Riveted. Rivet-holes drilled in place, i.e., Rivet-holes 
punched 1/4" small, courses rolled up, covering-plates bolted on courses. Heads in courses 
with all holes together perfectly fair. Then rivet-holes drilled to full size. 

Longitudinal braces without welds, with upset screw ends. 

Two (2) or three (3) Lugs on each side, and to be provided with wall-plates and expan- 
sion-rolls. Manhole (internal frame) on top. This frame a steel casting. 



Two (2) 5" Nozzle.? on top, 



A Hand-hole in each head, Fusible Safety Plug in back head. Bottom at back end 

reinforced and tapped for 2" blowout 

Internal Feed Pipe placed in Boiler Co.'s style, 

With Boiler, Castings for setting, viz.; C. I., Overhung Front, Mouth-pieces, 
Division Plates, Grate Bars, shaking pattern bo" X bo" . Grate Bearers, Ash-pit Door for 
the brickwork, Back Return Arched T Bars, the Anchor Bolts for Front. One (1) set of 

six (b) Buckstaves and Tie Rods with the boiler. With the Boiler One (1) 4" Pop 

Safety Valve, (3)3/4" Gauge Cocks, One (1) b" Steam Gauge, One (1)3/4" Water Gauge and 

One (1) Combination Column Boiler tested 223 lbs. per 

square inch. Inspected and Insured in the sum of $400.00 for one year, by '.. Steam 

Boiler Inspection & Insurance Co 

The Boiler Castings and Fixtures as herein specified by name, delivered F. O. B. cars, 
or at vessel's wharf, or on sidewalk of building, Boston, Mass., for the sum of six hundred 
and seventy {bjo.oo) dollars net. 

Very respectfully yours, 

IRON WORKS CO. 

P. S. — Specimens will be furnished, one lengthwise and one crosswise, from each plate. 
To be at least 18" long and planed on edge 1" or i\" wide. These specimens shall show no 
blowhole defects and shall bend double cold, at a red heat, and at a flanging heat. 



APPENDIX, 



• 39^ 



APPENDIX. 















HORIZONTAL RETURN TUBULAR 






Heat- 
ing- 
Surface 


Shell. 


Tubes. 




















Number. 


No. 


Horse- 
power. 


Diam- 
eter. 


Length, 
0. H. 


Length, 
Flush. 


Length, 


Diam- 
eter. 


With 
Man- 


With- 
out 
























hole. 


Man- 
hole. 


I 


21 


254 


36 


11 





11 





10 





3 




28 


r. 


25 


3°4 


36 


?3 





J 3 





12 





3 




28 


3 


33 


403 


42 


1 3 





13 





12 





3 




38 


4 


39 


469 


42 


15 





i5 





14 





3 




38 


5 


55 


604 


48 


15 


2 


15 


2 


14 





3 




50 


6 


62 


690 


48 


17 


2 


17 


2 


16 





3 




50 


7 


49 


548 


48 


i5 


2 


15 


2 


14 





3% 




38 


8 


56 


625 


48 


17 


2 


17 


2 


16 





3h 




38 


9 


67 


739 


54 


15 


2 


15 


2 


14 





3 




62 


IO 


76 


844 


54 


17 


2 


i7 


2 


16 





3 




62 


ii 


86 


949 


54 


19 


2 


19 


2 


18 





3 




62 


12 


64 


704 


54 


J 5 


2 


15 


2 


14 





3h 




5° 


13 


73 


803 


54 


*7 


2 


17 


2 


16 





3h 




50 


14 


82 


9°3 


54 


19 


2 


19 


2 


18 





3* 




5° 


15 


87 


875 


60 


15 


2 


15 


2 


14 





3 


74 


82 


l6 


99 


999 


.60 


17 


2 


17 


2 


16 





3 


74 


82 


17 


112 


1123 


60 


19 


2 


19 


2 


18 





3 


74 


82 


18 


76 


765 


60 


i5 


2 


IS 


2 


14 





3i 


54 


62 


T .9 


87 


873 


60 


17 


2 


17 


2 


16 





3h 


54 


62 


20 


98 


981 


60 


19 


2 


19 


2 


18 





3h 


54 


62 


21 


124 


1247 


66 


17 


6 


17 


2 


16 





3 


94 


104 


22 


140 


1 401 


66 


r 9 


6 


19 


2 


18 





3 


94 


104 


2 3 


155 


i55 6 


66 


21 


6 


21 


2 


20 


c 


3 


94 


104 


24 


"3 


1 133 


66 


i7 


6 


17 


2 


16 





3l 


72 


80 


2 5 


127 


1273 


66 


19 


6 


19 


2 


18 





3h 


72 


80 


26 


141 


1414 


66 


21 


6 


21 


2 


20 





3h 


72 


80 


27 


99 


996 


66 


17 


6 


17 


2 


16 





4 


54 


62 


28 


111 


1119 


66 


19 


6 


19 


2 


18 





4 


54 


62 


29 


124 


1242 


66 


21 


6 


21 


2 


20 





4 


54 


62 


30 


158 


1588 


72 


17 


6 


17 


2 


16 





3 


122 


130 


31 


178 


1785 


72 


19 


6 


19 


2 


18 





3 


122 


130 


3 2 


198 


1982 


72 


21 


6 


21 


2 


20 





3 


122 


130 


33 


144 


1448 


72 


17 


6 


17 


2 


16 





3^ 


94 


102 


34 


162 


1628 


72 


19 


6 


19 


2 


18 





3$ 


94 


102 


35 


180 


1807 


72 


21 


6 


21 


2 


20 





3§ 


94 


102 


36 


129 


1292 


72 


17 


6 


17 


2 


16 





4 


72 


80 


37 


145 


i45 2 


72 


19 


6 


19 


2 


18 





4 


72 


80 


38 


161 


1612 


72 


21 


6 


21 


2 


20 





4 


72 


80 


39 


209 


2090 


78 


19 


6 






18 





3 


144 


x 54 








40 

41 
42 

43 
44 
45 


232 

195 
216 


2321 

1952 
2167 
1821 


78 


21 


6 






20 





3 

3* 

3* 

4 


144 


x 54 


78 
78 
78 
78 
84 


19 
21 


6 




18 





114 


122 


6 




20 





114 


122 


182 


19 
21 


6 




18 





92 


100 


202 


2022 


6 




20 





4 


92 


100 


2.57 


2579 


19 


6 




18 





3 


180 


190 








46 

47 
48 


286 
236 
262 


2864 
2367 
2629 


84 
84 
84 


21 


6 






20 





3 

3? 

3* 


180 


190 


19 
21 


6 




18 





140 


!5 


6 




20 





140 


150 






49 


215 


2i55 


84 


19 


6 






18 





4 


no 


114 








50 


239 


2302 


84 


21 


6 






20 





4 


no 


114 







APPENDIX 
BOILERS. (Robb-Mumford Boiler Co.) 



397 



Thickness, 
125 Pounds. 


Thickness. 
150 Pounds. 




Grates. 




Weights. 








Size 
of 














































Safety 












Shell. 'Heads 

1 


Style 
Joint. 


Shell. 


Heads 


Style 
Joint. 


Valve 


Width 


L'gth 


Boiler 
Only. 


Castings. 


Total. 


1/4 

1/4 


3/8 
3/8 


D.L. 








2 


36 
36 


30 
36 


2730 
3120 


2030 

2080 


4760 

5200 


D.L. 


..... 


.... 


. . 


2 


5/i6 


3/8 


D.B. 


11/32 


3/8 


D.B. 


2 


42 


36 


4670 


2670 


7340 


5/l6 


3/8 


D.B. 


11/32 


3/8 


D.B. 


2 


42 


42 


5270 


2740 


8010 


11/32 


7/16 


D.B. 


13/32 


7/16 


D.B. 


2| 


48 


42 


6800 


3540 


10340 


11/32 


7/16 


D.B. 


13/32 


7/16 


D.B. 


A 


48 


48 


758o 


4000 


1 1 580 


11/32 7/16 D.B. 


13/32 


7/16 


D.B. 


2h 


48 


42 


6740 


3540 


10280 


11/32 7/16 j D.B. 


13/32 


7/16 


D.B. 


*\ 


48 


48 


7520 


4000 


11520 


11/32 


7/16 T.B. 


13/32 


7/16 


T.B. 


2* 


54 


48 


8120 


4300 


12420 


11/32 


7/16 T.B. 


13/32 


7/16 


T.B. 


3 


54 


54 


9100 


4770 


13870 


11/32 


7/i6 T.B. 


13/32 


7/16 


T.B. 


3 


54 


60 


1 0000 


5I90 


15190 


11/32 


7/16 j T.B. 


13/32 


7/16 


T.B. 


2\ 


54 


48 


8210 


4300 


12510 


11/32 


7/16 T.B. 


13/32 


7/16 


T.B. 


3 


54 


54 


9210 


4770 


13980 


11/32 


7/16 T.B. 


13/32 


7/16 


T.B. 


3 


54 


60 


10120 


5*9° 


IS3IO 


3/8 


1/2 


Q.B. 


7/16 


1/2 


Q.B. 


3 


60 


54 


10270 


4920 


15190 


3/8 


1/2 


Q.B. 


7/i6 


1/2 


Q.B. 


3 


60 


60 


11420 


53°° 


16720 


3/8 


1/2 


Q.B. 


7/16 


1/2 


Q.B. 


3 


60 


66 


12480 


594o 


18420 


3/8 


1/2 


Q.B. 


7/16 


1/2 


Q.B. 


3 


60 


54 


10060 


4920 


14980 


3/8 


1/2 


Q.B. 


7/16 


1/2 


Q.B. 


3 


60 


54 


1 1 180 


5i7 


16250 


3/8 


1/2 


Q.B. 


7/l6 


1/2 


Q.B. 


3 


60 


60 


12200 


579o 


17990 


I3/3 2 


1/2 


Q.B. 


15/32 


1/2 


Q.B. 


3 


66 


60 


14500 


579o 


20290 


I3/3 2 


1/2 


Q.B. 


J 5/32 


1/2 


Q.B. 


3\ 


66 


66 


1593° 


6410 


22340 


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1/2 


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15/32 


1/2 


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3\ 


66 


72 


17380 


6540 


23920 


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66 


60 


14410 


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3 


66 


60 


15840 


6170 


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3\ 


66 


66 


17270 


6410 


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1/2 


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3 


66 


60 • 


14210 


579° 


20000 


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66 


60 


15610 


6170 


21780 


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3 


66 


60 


17020 


6170 


23190 


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72 


66 


17170 


6540 


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72 


72 


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7290 


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4 


72 


84 


20650 


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72 


66 


17100 


6540 


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32 


72 


72 


18820 


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26110 


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35 


72 


78 


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16960 


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23500 


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66 


18670 


7150 


25820 


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72 


72 


20390 


7290 


27680 


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78 


90 


24620 


8860 


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78 


78 


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8550 


31260 


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78 


84 


24770 


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28100 


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84 


25670 


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Ah 


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90 


28070 


9620 


37690 


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78 


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1/2 


9/16 


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5/8 


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Ah 


90 


84 


28110 


0440 


3755o 



398 



APPENDIX. 




APPENDIX. 



399 



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M 



APPENDIX 



401 



Stirling Boilers. — These boilers clean from the side, the 
same as the B. & W., and only two can be set together without a 
space between. If necessary the boiler may be set without a 
space at the back, but it is advisable to have at least 3 feet 
back of the rear wall. 

These boilers are also built with attached superheaters. The 
superheater is placed at different parts of the setting, according 
to the number of degrees of superheating desired. 

The following table gives dimensions of this boiler for different 
boiler horce-powers. 

If the boiler is equipped with a superheater, deduct 10 per 
cent from the rated horse-power. If, however, the superheater 
is flooded the capacity of the boiler is increased approximately 
7 per cent above the ratings giver.. 



HORSE-POWER OF STIRLING BOILERS. 

Arranged with Reference to Height and Width of Settings. 







Class. 


Width r 






















Sett 


ing. 


B-low. 


F 


1 E 


B 


1 A | Q 


1 F 


1 K 


K 


L 


N 




Height. 




Bat- 
tery.* 

feet. 


11' 11" 


i5'4i" 


Us' 3" 


|r S ' 8" 


|i8' 9"|i8'io' 


I20' 7' 


I20' 8" 


2l'l0" 


U*' 4" 


24' 6" 


Single. 










Depth 












ft in. 


14' 0" 


18' 7" 




14' 0" 


1 
16' 0" 18' 9" 


16' 9" 


18' 2" 


17' 7" 


iS' 3" 


18 10" 


S 6 


10 


5° 






So 
















6 


11 


55 




75 


60 
















6 6 


12 


65 




90 


7° 
















7 


13 


75 


115 


100 


80 


115 


145 


140 


145 


I.SO 


IO.S 


175 


7 


14 


85 


130 


115 


90 


13° 


165 


155 


160 


I70 


I«5 


195 


8 


15 


■ 95 


145 


125 


100 


145 


180 


175 


180 


i»5 


205 


220 


8 6 


16 


*°5 


160 


140 


no 


160 


200 


190 


200 


205 


230 


240 


9 


17 


115 


175 


150 


120 


175 


215 


205 


215. 


225 


250 


260 


9 


18 


i^5 


190 


165 


130 


190 


235 


225 


235 


245 


270 


2«5 


10 


19 


135 


205 


i75 


140 


205 


255 


240 


250 


260 


290 


3°5 


10 6 


20 


140 


220 


190 


150 


215 


270 


260 


270 


280 


310 


33° 


11 


21 


150 


230 


200 


160 


230 


290 


275 


2«5 


300 


33° 


35o 


11 6 


22 


160 


245 


215 


170 


245 


310 


295 


305 


315 


35o 


37o 


12 


23 


170 


260 


225 


1 So 


260 


325 


310 


3-5 


335 


31° 


393 


12 6 


24 


180 


275 


240 


190 


275 


345 


33° 


34o 


355 


395 


4i5 


13 


2 5 


190 


290 


250 


200 


290 


360 


345 


360 


375 


415 


435 


13 6 


26 


200 


3°5 


265 


210 


305 


380 


360 


375 


39° 


435 


460 


14 


27 


210 


320 


275 


220 


320 


3 co 


380 


395 


410 


455 


480 


14 6 


28 


220 


335 


290 


230 


335 


4i5 


395 


410 


43° 


475 


505 


15 


29 


230 


35o 


300 


240 


35o 


435 


4L5 


43° 


45o 


495 


525 


15 


3° 


, 240 


395 


3i5 


250 


360 


45° 


43° 


45° 


<6 5 


5i5 


-545 


16 


3i 


250 


375 


33° 


260 


375 


470 


45o 


465 


48.S 


54° 


57o 


16 6 


3 2 


260 


39° 


340 


270 


39° 


490 


465 


485 


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560 


59o 


17 


33 


265 


405 


355 


280 


405 


505 


485 


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520 


580 


610 


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34 


275 


420 


365 


290 


420 


525 


500 


520 


540 


600 


635 


18 


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285 


435 


380 


300 


435 


545 


5i5 


540 


560 


620 


t>55 



* The horse-power is double for battery width shown. Single boilers require an 
alley on one side; battery boilers require an alley on both sides. 



402 APPENDIX. 

Heine Water Tube Boiler. — This boiler requires a space at 
the back as it is cleaned from the ends. Any number of boilers of 
this type can be set side by side. 

The space in front of the boiler should be sufficient to allow of the 
renewal of a tube. 

The accompanying table together with the "Notes" will serve to 
give necessary sizes for a given boiler horse-power. 

Notes. 

The length of setting from fire front to rear of brickwork. is always 
i foot 4 inches longer than the length of the tubes, for instance, the 
setting of a 90 horse-power boiler is 17 feet 4 inches long and a 101 horse- 
power boiler is 19 feet 4 inches long. The shell with manhead extends 
about 15 inches beyond rear of setting, so that if possible a 4-foot space 
should be allowed behind the setting for access to same. In special 
cases the manhole is placed in the front head, or an opening may be 
made in the building wall opposite manhole, in which case 2 feet 
behind setting will be sufficient. The width of setting may be deter- 
mined by adding the thickness of brick walls to the width of furnace. 
Thus, three 101 horse-power boilers in a batterv, with 19 inches side 
and 28 inches division walls, will be 19"+ 53"+ 28"+ 53"+ 28"+ 53" 
+ i9 // =2i / i" '. Existing walls may be utilized where space is limited, 
and the outside walls here reduced to a furnace lining 9 or 10 inches 
thick. 

The grate-surface given for bituminous coal is such that the rating 
may be e?.sily developed with a 1/2-inch draught at the smoke outlet. 
The grate area given for anthracite pea coal is that necessary in order 
to develop the rating of the boiler with 1/2-inch draught at the smoke 
outlet. For convenience cf handling it is advisable to limit the grate 
length for anthracite coal to 7 feet 6 inches. Where this does not give 
area enough for the desired maximum capacity it is necessary to in- 
crease the draught. Standard grate lengths are 6 feet 6 inches, 7 feet 
and 7 feet 6 inches. 

Safety-valves are provided as required to meet local inspection laws. 



Babcock and Wilcox Boilers. — These boilers clean from the 
side. There must be a space of at least 5 feet between each set of two. 

The tables on pages 405 and 406 give space taken up by boilers with 
vertical headers. For inclined headers, any number of tubes high, add 
3 feet 8 inches to the length given. 

A double-deck boiler is 10 inches higher than a single-deck boiler 
of same number of tubes high. 

Space must be left in front of the boiler to enable the lowest tube to 
be replaced. 



APPENDIX. 



403 



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404 



APPENDIX. 



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406 



APPENDIX. 



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APPENDIX. 
GREEN'S FUEL ECONOMIZER. 



407 









Dimensions, 


Area between 






£ 




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1344 


6,944 


1 


2 


i.S 


128 


4 


19- 4 
























32 


1536 


7,936 


1 


2 


i-5 


144 


4 


21— 9 
























36 


1728 


8,928 


1 


2.5 


2 


160 


4 


24— 2 
























40 


1920 


9,920 


2 


2.5 


2 


176 


4 


26-7 
























44 


2112 


10,912 


2 


2.5 


2 


192 


4 


29- 
























48 


2304 


11.904 


2 


2.5 


2 


208 


4 


3i- 5 














52 


2496 


12,896 


2 


2.5 


2 


48 


6 


4-10 


4-8 


5-5 


6-2 


21.85 


29. 10 


36,35 


8 


576 


2,976 


•5 


2 


i-5 


72 


6 


7- 3 


























12 


864 


4,464 


• 5 


2 


i-S 


96 


6 


9- 8 


























16 


1152 


5,852 


1 


2 


i-S 


120 


6 


12- 1 


























20 


1440 


7,440 


1 


2 


i-5 


144 


6 


14-6 


























24 


1728 


8,928 


1 


2.5 


2 


168 


6 


16— 11 


























28 


2016 


10,416 


2 


2.5 


2 


192 


6 


19- 4 


























32 


2304 


1 1,904 


2 


2.5 


2 


216 


6 


21-9 


























36 


2592 


13,392 


2 


2.5 


2 


240 


6 


24-2 


























40 


2880 


14,880 


2 


2.5 


2 


264 


6 


26— 7 


























44 


3168 


16,368 


2-5 


2.5 


2 


288 


6 


29-0 


























48 


3456 


17,856 


2.5 


2.5 


2 


312 


6 


3i-5 


























52 


3744 


19,344 


2-5 


2.5 


2 


336 


6 


33-io 


























56 


4032 


20,832 


2 -5 


2-5 


2 


360 


6 


36- 3 














60 


4320 


22,320 


3 


3 


2.S 


96 


8 


7- 3 


6-0 


6-9 


7-6 


27 .00 


34.25 


4I.-.5 


12 


1152 


5,952 


1 


2 


i-S 


128 


8 


9- 8 
























16 


1536 


7,936 


1 


2 


i-S 


160 


8 


12- 1 
























20 


1920 


9,920 


2 


2.5 


2 


192 


8 


14- 6 
























24 


2304 


11,904 


2 


2.5 


2 


224 


8 


1 6-1 1 


" 






















28 


2688 


13,888 


2 


2-5 


2 


256' 


8 


19- 4 


" 






















32 


3072 


15,872 


2 


2-5 


2 


288 


8 


21—9 


" 






















36 


3456 


17,856 


2-5 


2.5 


2 


320 


8 


24—2 
























40 


3840 


19,840 


2-5 


2.5 


2 


352 


8 


26— 7 
























44 


4224 


21,824 


2.5 


3- 


2-5 


384 


8 


29-0 
























48 


4608 


23,808 


2.5 


3 


2-5 


416 


8 


3i- 5 
























52 


4992 


25,792 


2-5 


3 


2 -S 


448 


8 


33-IO 
























56 


5376 


27,776 


3 


3 


2 -5 


480 


8 


36- 3 














60 


576o 


29,760 


3 


3 


2-S 


160 


10 


9- 8 


7-4 


S ~ J 


8-10 


32-25 


3 9- .50 


46,75 


16 


1920 


9,920 


2 


2-5 


2 


200 


10 


12- 1 
























20 


2400 


12,400 


2 


2-5 


2 


240 


10 


14- 6 


" 






















24 


2800 


14,880 


2 


2 -5 


2 


280 


10 


16-11 
























28 


336o 


17,360 


25 


2.5 


2 


320 


TO 


19- 4 
























32 


3840 


19,840 


2-5 


3- 


2-S 


360 


IO 


21-9 
























36 


4320 


22,320 


2-5 


3. 


2-S 


400 


IO 


24—2 
























40 


4800 


24,800 


2.5 


3- 


2-5 


440 


IO 


26-7 
























44 


5280 


27,780 


2.5 


3- 


2-S 


480 


IO 


29-0 
























48 


576o 


29,780 


2-5 


3- 


2-S 


520 


IO 


31- S 
























52 


6240 


32,240 


3 


3- 


2-S 


560 


IO 


33-io 
























56 


6720 


34,720 


3 


4- 


3 


600 


IO 


36- 3 


" 






















60 


7200 


37,200 


3 


4. 


3 


640 


IO 


38- 8 
























64 


7680 


39,680 


3 


4. 


3 


680 


IO 


41- 1 


" 






















68 


8160 


42,160 


3 


4- 


3 


720 


IO 


43- 6 


" 






















72 


8640144,640 


4-5 


4. 


3 


760 


IO 


45-11 
























76 


9120 47,120 


4-5 


4. 


3 


800 


IO 


48~ 4 














80 


9600)49,600 
1 


5 


4. 


3 



4 o8 








APPENDIX. 




















STANDARD 


SIZES OF STURTEVANT 






No. 




ternal 


Capacity 


General Dimensions. 










Height in Feet and 


Ma- 


No. 


No. of 


Heat- 


in 








Inches. 


chine 
No. 


of 
Pipes. 


of 


Pipes in 
Section. 




Pounds 




Width. 




Sec- 
tions. 


mg- 
3urface. 


of 
Water. 






Section. 


Section 
and 










Sq. ft. 




Ft. 


In. 


Ft. In. 




Gearing. 


I 


3 2 


8 


4 


400 


2,016 


4 


10 


3 2* 


IO 2\ 


12 6 


2 


48 


12 


4 


600 


3>° 2 4 


7 


3 


( < 


i i 


" 


3 


64 


16 


4 


801 


4,032 


9 


8 


1 < 


1 1 


" 


4 


80 


20 


4 


IOOI 


5,040 


12 


1 


< i 


1 i 


" 


5 


96 


24 


4 


1 201 


6,048 


14 


6 


t t 


i i 


" 


6 


112 


28 


4 


1401 


7,056 


16 


11 


c t 


i i 


" 


7 


128 


32 


4 


1601 


8,064 


19 


4 


'■' 


" 


" 


8 


40 


8 


5 


499 


2,520 


4 


10 


3 10J 


IO 2\ 


12 6 


9 


60 


12 


5 


749 


3,78o 


7 


3 


( ( 


i 1 


" 


IO 


80 


16 


5 


999 


5,040 


9 


8 


(I I I 


it 


ii 


100 


20 


5 


1248 


6,300 


12 


1 


I I 


i 1 


t i 


12 


120 


24 


5 


1499 


7,56o 


14 


6 


i c 


1 1 


1 1 


13 


140 


28 


5 


1747 


8,820 


16 


11 


( 1 


1 1 


1 1 


14 


160 


32 


5 


1997 


10,080 


19 


4 


( 1 


1 i 


1 1 


15 


180 


36 


5 


2247 


n,340 


21 


9 


1 ' 


" 


1 1 


16 


200 


40 


5 


2496 


12,600 


24 


2 


" 


" 


1 1 


i7 


72 


12 


6 


897 


4,53 6 


7 


3 


4 6i 


IO 2\ 


12 6 


18 


96 


16 


6 


1196 


6,048 


9 


8 


" 


1 1 


11 


19 


120 


20 


6 


1496 


7,56o 


12 


1 


1 I 


1 1 


c 1 


20 


144 


24 


6 


1795 


9,072 


14 


6 


I I 


1 1 


C ( 


21 


168 


28 


6 


2094 


10,584 


16 


11 


I I 


1 1 


( ( 


22 


192 


32 


6 


2393 


12,096 


19 


4 


" 


i t 


it 


23 


216 


36 


6 


2692 


13,608 


21 


9 


I ( 


1 1 


1 1 


24 


240 


40 


6 


2991 


15,120 


24 


2 


' ' 


1 i 


1 1 


25 


264 


44 


6 


3290 


16,632 


26 


7 


" 


1 1 


tt 


26 


288 


48 


6 


3589 


18,144 


29 





« I 


tt 


1 1 


27 


112 


16 


7 


1394 


7,056 


9 


8 


5 A 


IO 2\ 


12 6 


28 


140 


20 


7 


1743 


8,820 


12 


1 


t I 


1 1 


« ( 


29 


168 


24 


7 


2092 


10,584 


14 


6 


t t 


tt 


II 


3° 


196 


28 


7 


2440 


12,348 


16 


11 


" 


tt 


1 1 


3 1 


224 


32 


7 


2789 


14,112 


19 


4 


' ' 


1 1 


1 1 


3 2 


252 


36 


7 


3*37 


15,876 


21 


9 


" 


tt 


tt 


33 


280 


40 


7 


3486 


17,640 


24 


2 


t t 


tt 


tt 


34 


308 


44 


7 


3835 


19,404 


26 


7 


t t 


tt 


tt 


35 


33 6 


48 


7 


4183 


21,168 


29 





I t 


1 1 


tt 


36 


3 6 4 


52 


7 


4532 


22,932 


3i 


5 


i t 


t < 


tt 


37 


392 


56 


7 


4880 


24,696 


33 


10 


t ( 


(< 


tt 


38 


128 


16 


8 


i59 2 


8,064 


9 


8 


5 i°J 


IO 2\ 


12 6 


39 


160 


20 


8 


1990 


10,080 


12 


1 


( ( 


tt 


it 


40 


192 


24 


8 


2388 


12,096 


14 


6 


'* 


tt 


1 1 


41 


224 


28 


8 


2786 


14,112 


16 


11 


11 


tt 


1 1 


42 


256 


32 


8 


3185 


16,128 


19 


4 


tt 


tt 


tt 


43 


288 


36 


8 


3583 


18,144 


21 


9 


It 


1 1 


i I 


44 


320 


40 


8 


398i 


20,160 


24 


2 


ii 


1 1 


11 


45 


352 


44 


8 


4379 


22,176 


26 


7 


i I 


' ' 


I I 


46 


384 


48 


8 


4777 


24,182 


29 





ii 


< « 


1 1 


47 


416 


52 


8 


5i75 


26,198 


3i 


5 


11 


" 


1 1 


48 


448 


56 


8 


5573 


28,224 


33 


10 


1 1 


'* 


1 1 


49 


480 


60 


8 


597i 


30,240 


36 


3 


I ( 


tt 


1 1 

1 



APPENDIX. 



409 



"STANDARD 


ECONOMIZERS. 


















No. 
of 




Ex- L ., 
ternal Capacity 


General Dimensions. 










Height in Feet and 


Ma- 
chine 
No. 


No. 


No. of 
Pipes in 
Section. 


Heat- 1 „ in , 
ing- 1 Pounds 

surface. „- ot 

} Water. 


T nn nr-f Y\ 


Width. 


Inches. 


Pipes. 


Sec- 
tions. 






Section. 


Section 
and 










Sq. ft. I 


Ft. 


In. 


Ft. In 




Gearing. 


5° 


180 


20 


9 


2,237 1 11,340 


12 


I 


6 6£ 


IO 2j 


12 6 


5i 


216 


'24 


9 


2,685 1 13,608 


14 


6 




" ' 


' ' 


52 


252 


28 


9 


3,132 ; 15,876 


16 


11 




' ' 


' ' 


53 


288 


3 2 


9 


3,580 j 18,144 


19 


4 




' ' 


1 ' 


54 


324 


36 


9 


4,027 • 20,412 


21 


9 




' ' 




55 


360 


40 


9 


4,475 22,680 


24 


2 




' ' 


' ' 


56 


39 6 


44 


9 


4,922 24.948 


26 


7 




« < 


" 


57 


432 


48 


9 


5,370 27,216 


29 







** 


4 ' 


58 


468 


52 


9 


5,817 29,484 


31 


5 




' ' 


' ' 


59 


504 


56 


9 


6,265 


3i,752 


33 


10 




1 i 


1 < 


60 


540 


60 


9 


6,712 


34,020 


36 


3 




" 


< < 


61 


576 


64 


9 


7,160 


36,288 


38 


8 




'* 


1 ■ 


62 


200 


20 


10 


2,484 


12,600 


12 


1 


7 A 


IO 2\ 


12 6 


63 


240 


24 


10 


2,981 


15,120 


14 


6 




11 


1 1 


64 


280 


28 


10 


3,478 


17,640 


16 


11 




* ' 


< 1 


65 


320 


32 


10 


3,974 


20,160 


19 


4 




" 


< t 


66 


360 


36 


10 


4,471 


22,680 


21 


9 




' ' 


'* 


67 


400 


40 


10 


4,968 


25,200 


24 


2 


* " 


1 1 


68 


440 


44 


10 


5,465 


27,720 


26 


7 




' ' 


< < 


69 


480 


48 


10 


5,962 30,240 


29 







" 


• < 


70 


520 


52 


10 


6,458 32,760 


3i 


5 




* ' 


" 


7i 


560 


56 


10 


6,955 35.280 


33 


10 




t 1 


< < 


72 


600 


60 


10 


7,452 37,800 


36 


3 




" 


> « 


73 


640 


64 


10 


7,949 


40,320 


38 


8 




" 


" 


74 


680 


68 


10 


8,446 


42,840 


41 


1 




< i 


' ' 


75 


396 


36 


11 


4,915 


24,949 


21 


9 


7 jo\ 


IO 2\ 


12 6 


76 


440 


40 


11 


5,461 


27,720 


24 


2 




1 4 


f • 


77 


484 


44 


11 


6,008 


3°>497 


26 


7 




" 


" 


78 


528 


48 


11 


6,554 


33,268 


29 







< 1 


< < 


79 


572 


52 


11 


7,101 


36,045 


3i 


5 




t < 


< < 


80 


616 


56 


11 


7,646 


38,811 


33 


10 




c c 


1 c 


81 


660 


60 


11 


8,193 


41,588 


36 


3 




< < 


I < 


82 


704 


64 


11 


8,739 


44,359 


38 


8 




1 ' 


" 


83 


748 


68 


11 


9,286 


47,136 


41 


1 




1 < 


n 


84 


792 


72 


11 


9,832 


49,907 


43 


6 




ta 


" 


85 


836 


76 


11 


IO ,379 


52,684 


45 


11 




•< 


" 


86 


880 


80 


11 


10,925 


55,455 


48 


4 




' ' 


( 1 


87 


528 


44 


12 


6,549 


33,262 


26 


7 


8 t 6* 


IO 2\ 


12 6 


88 


576 


48 


12 


7,i45 


36,289 


29 







•■' 


(« 


89 


624 


52 


12 


7,74i 


39,317 


3i 


5 




' ' 


" 


90 


672 


56 


12 


8,337 


42,344 


33 


10 




" 


t < 


9i 


720 


60 


12 


8,933 


45,37i 


36 


3 




( 1 


< ( 


92 


768 


64 


12 


9,529 


48,398 


38 


8 




< ( 


** 


93 


816 


68 


12 


10,125 


51,425 


41 


1 




*' 


" 


94 


864 


72 


12 


10,721 


54,452 


43 


6 




' ' 


' ' 


95 


912 


76 


12 


",3i7 


57,479 


45 


11 




t i 


" 


96 


960 


80 


12 


",9i3 


60,506 


48 


4 




1 1 


t < 


97 


1008 


84 


12 


12,489 


63,432 


5o 


9 




" 


<f 


98 


1056 


88 


12 


13,065 


66,357 


53 


2 




« « 


• « 



4TO 



APPENDIX. 
LOGARITHMS. 



Nat 






















Proportional Parts. 


Nos'. 





1 


2 


3 


4 


5 


6 


7 


8 


9 


































1 2 


3 


4 


5 


6 


7 8 9 


10 


0000 


0043 


0086 


0128 


0170 


0212 


0253 


0294 


0334 


0374 


4 8 


12 


17 


21 


25 


29 33 37 


11 


0414 


0453 


0492 


0531 


0569 


0607 


0645 


0682 


0719 


0755 


4 8 


11 


15 


19 


23 


26 30 34 


12 


0792 


0828 


0864 


0899 


0934 


0969 


1004 


1038 


1072 


tio6 


3 7 


10 


U 


17 


21 


24 28 31 


13 


ii39 


H73 


1206 


1239 


1271 


1303 


1335 


1367 


J399 


1430 


3 6 


10 


13 


16 


19 


23 26 29 


14 


1 46 1 


[492 


1523 


1553 


1584 


1614 


1644 


1673 


1703 


1732 


3 6 


9 


12 


15 


iS 


21 24 27 


15 


[761 


1790 


1S18 


1847 


1875 


1903 


i93i 


1959 


1987 


2014 


3 6 


8 


11 


14 


17 


20 22 25 


16 


2041 


2068 


2095 


2122 


2148 


2175 


2201 


2227 


2253 


2279 


3 5 


8 


1 1 


13 


16 


18 21 24 


17 


2304 


2330 


2355 


23S0 


2405 


2430 


2455 


2480 


2504 


2529 


2 5 


7 


10 


12 


15 


17 20 22 


18 


2553 


2577 


2601 


2625 


2648 


2672 


2695 


2718 


2742 


2765 


2 5 


7 


9 


12 


14 


t6 19 21 


19 


2788 
3010 


2810 


2833 


2856 


2878 


2900 
3118 


2923 
3^39 


2945 
3160 


2967 
3181 


2989 
3201 


2 4 


7 


9 


11 


13 


16 18 20 


20 


3032 


3054 


3075 


3096 


2 4 


6 


8 


11 


13 


15 17 19 


21 


3222 


3243 


3263 


3284 


3304 


3324 3345 


3365 


3385 


3404 


2 4 


6 


8 


10 


12 


14 16 18 


22 


3424 


3444 


3464 


3483 


3502 


3522 


354i 


356o 


3579 


3598 


2 4 


6 


8 


10 


12 


14 15 '7 


23 


3617 


3636 


3655 


3674 


3692 


37ii 


3729 


3747 


3766 


3784 


2 4 


6 


7 


9 


11 


13 15 17 


24 


3802 


3820 


38383856 


3874 


3892 


3909 


3927 


3945 


3962 


2 4 


5 


7 


9 


11 


12 14 s6 


25 


3979 


3997 


4014 


4031 


4048 


4065 


4082 


4099 


4116 


4133 


2 3 


c 


7 


9 


10 


12 14 15 


26 


415c 


4166 


4183 


4200 


4216 


4232 


4249 


4265 


4281 


4298 


2 3 


5 


7 


8 


10 


" 13 15 


27 


43M 


4330 


4346 


4362 


4378 


4393 


4409 


442 5 


44404456 


2 3 


5 


6 


8 


9 


II 13 14 


28 


4472 


4487 


4502 


45i8 


4533 


4548 


4564 


4579 


4594 4609 


2 3 


5 


6 


8 


9 


II 12 14 


29 


4624 
4771 


4639 
4786 


4654 


4669 


4683 


4698 


4713 


4728 


4742 


4757 


1 3 


4 


6 

6 


7 
7 


9 
9 


IO 12 13 


30 


4800 


4814 


4829 


4843 


4857 


4871 


4886 


4900 


1 3 


4 


TO II 13 


31 


49M 


492S 


4942 


4955 


4969 


4983 


4997 


5011 


5024 


5038 


' 3 


4 


6 


7 


S 


IO II 12 


32 


5051 


5065 


5079 


5092 


5105 


5ii9 


5132 


5145 


5I595I72 


1 3 


4 


5 


7 


8 


9 II !2 


33 


5185 


519S 


5211 


5224 


5237 


52505263 


5276 


52895302 


1 3 


4 


5 


6 


8 


9 IO 12 


34 


5315 


5328 


53405353 


5366 


53785391 


5403 


5416,5428 


1 3 


4 


5 


6 


S 


9 IO II 


35 


544i 


5453 


5465 5478 


5490 


5502 5514 


5527 


5539 5551 


t 2 


4 


5 


6 


7 


9 IO II 


36 


5563 


5575 


5587 


5599 


5611 


5623 5635 


5647 


5658 


5670 


1 2 


4 


5 


6 


7 


8 10 11 


37 


5682 


5694 5705 


5717 


5729 


57405752 


5763 


5775 


5786 


r 2 


3 


5 


6 


7 


8 9 10 


38 


579S 


5809 5S21 


5832 


5843 


5855 


5866 


5877 


58S8 


5899 


1 2 


3 


5 


6 


7 


8 9 TO 


39 


59ii 
6021 


5922 5933 
6o3i'6o42 


5944 


5955 


5966 


5977 


5988 


5999 


6010 


1 2 


3 


4 


5 


7 


8 9 10 


40 


6053 


6064 


6075 


6085 


6096 


6107 


6117 


1 2 


3 


4 


5 


6 


8 9 10 


41 


612S 


6138:6149 


6160 


6170 


6180 6191 


6201 


6212,6222 


1 2 


3 


4 


5 


6 


7 8 9 


42 


6232 


6243:6253 


6263 


6274 


6284*6294 


6304 


63146325 


1 2 


3 


4 


5 


6 


7 8 9 


43 


6335 


6345 6355 


6365 


6375 


63S56395 


6405 


6415J6425 


1 2 


3 


4 


5 


6 


7 8 9 


44 


6435 


644416454 


6464 


6474 


64846493 


6503 


651316522 


1 2 


3 


4 


5 


6 


7 8 9 


45 


6532 


6542 6551 


6561 


6571 


6580 6590 


6599 


6609 ! 66f8 


1 2 


3 


4 


5 


6 


7 8 9 


46 


662S 


6637,6646 


6656 


6665 


6675 6684 


6693 


6702 6712 


1 2 


3 


4 


5 


6 


7 7 8 


47 6721 


67306739 


6749 


6758 


6767,6776 


6785 


67946803 


1 2 


3 


4 


5 


5 


678 


48 6812 


6S21 6830 


6839 


6848 


68576866 


6875 


68846893 


1 2 


3 


4 


4 


5 


678 


49 6902 


691 1 
6998 


6920 


6928 


6937 


6946 


6955 


6964 


6972 6981 
7059 7067 


i 2 
1 2 


3 
3 


4 


4 


5 


678 


50 6990 


7007 


7016 


7024 


7033 


7042 


7050 


3 


4 


5 


678 


51 7076J7084 7093 

52 7160I7168 7177 

53 7243:725117259 


7101 


7110 


7118 7126 


7135 


7i437 ! 52 


1 2 


3 


3 


4 


c 


•678 


7185 


7193 


7202I7210 


7218 


7226 7235 


1 2 


2 


3 


4 


5 


6 7 7 


7267 


7275 


7284^292 


7300 


730S 7316 


1 2 


2 


3 


4 


5 


667 


54 


7324 


7332 


7340 


7348 


7356 


7364 


7372 


738o 


7388 


I7396 


1 2 


2 


3 


4 


5 


667 



APPENDIX. 
LOGARITHMS. 



411 








1 


2 


3 


4 


5 


6 


7 


8 


9 


Proportional Parts. 


Nos 




1 


7404 




















12 3 


4 5 6 7 8 9 


55 


7412 


7419 


7427 


7435 


7443 


745i 


7459 


7466 


7474 


122 


3 4 5 


5 6 7 


56 


7482 


7490 


7497 


7505 


7513 


7520,7528 


7536 


7543 


755i 


122 


3 4 5 


5 6 7 


57 


7559 


7566 


7574 


7582 


7589 


7597 


7604 


7612 


7619 


7627 


1 2 2 


3 4 5 


5 6 7 


58 


7634 


7642 


7649 


7657 


7664 


7672 


7679 


7686 


7694 


7701 


112 


3 4 4 


5 6 7 


59 


7709 


7716 


7723 


773' 


7738 


7745 


775* 


7760 


7767 


7774 


112 


3 4 4 


5 6 7 


60 


7782 


7789 


7796 


7803 


7810 


7818 


7825 


7832 


7839 


7846 


1 1 2 


3 4 4 


5 6 6 


61 


7853 


7860 


7868 


7875 


7882 


7889 


7896 


7903 


7910 


7917 


112 


3 4 4 


5 6 6 


62 


7924 


793i 


7938 


7945 


7952 


7959 


7966 


7973 


7980 


7987 


1 1 2 


3 3 4 


5 6 6 


63 


79Q3 


8000 


8007 


S014 


8021 


8028 


8035 


8041 


8048 


8055 


112 


3 3 4 


5 5 6 


64 


8062 
812c, 


S069 
Si 36 


8075 


8082 


8o8y 


8096 


8102 


8109 


8116 


8122 


112 


3 3 4 


5 5 6 


65 


8142 


8149 


8156 


8162 


8160 


8176 


8182 


8189 


1 1 2 


3 3 4 


5 5 6 


66 


8195 


8202 


8209 


8215 


8222 


S228 


8235 


8241 


8248 


8254 


112 


3 3 4 


5 5 6 


87 


8261 


8267 


8274 


8280 


82878293 


8299 


8306 


8312 


8319 


112 


3 3 4 


5 5 6 


68 


S325 


833' 


8338 


8344 


3351 


83578363 


S370 


8376 


8382 


112 


3 3 4 


4 5 6 


69 


S388 


8395 


8401 


8407 


8414 


8420 


8426 


8432 


8439 


8445 


112 


2 3 4 


4 5 6 


70 


8451 


8457 


8463 


3470 


8476 


8482 


8488 


8494 


8500 


8506 


112 


2 3 4 


4 5 6 


71 85i3 


8519 


8525 


853' 


8537 


8543 


8549 


8555 


8561 


8567 


112 


2 3 4 


4 5 5 


72 18573 


8579 


8585 


8591 


8597 


8603 


8609 


861c; 


362^ 


8627 


1 1 2 


2 3 4 


4 5 5 


73 663^ 


8639 


8645 


8651 


8657 


8663 


8669 


8675 


8681 


8686 


1 1 2 


2 3 4 


4 5 5 


74 8692 


869S 
3756 


8704 8710 
8762 8/68 


8716 
S774 


8722 


8727 


8733 


3739 


8745 


112 


2 3 4 


4 5 5 


75 


8751 


S779S785 


8791 


8797 


8802 


112 


2 3 3 


4 5 5 


76 


8808 


38 14 


8820 


882^ 


8831 


88378842 


8848 


8854 


8859 


1 1 2 


2 3 3 


4 5 5 


77 


8865 


8871 


8S76 


8882 


8887 


8893 


8899 


8904 


8910 


8915 


112 


2 3 3 


4 4 5 


78 


8921 


3927 


8932 


8938 


8943 


8949 


8954 


8960 


8965 


8971 


1 1 2 


2 3 3 


4 4 5 


79 


8976 


8982 


8987 


8993 


8998 


9004 


9009 


9015 


9020 


9025 


112 


2 3 3 


4 4 5 


80 


9031 


9036 


9042 


9047 


9053 


9058 


9063 


9069 


9074 


9079 


112 


2 3 3 


4 4 5 


81 


9085 


9090 


9096 


9101 


9106 


9112 


9117 


9122 


9128 


9133 


1 1 2 


2 3 3 


4 4 5 


82 


9138 


9M3 


9149 


9*54 


9159 


9165 


9170 


9175 


9180 


9186 


112 


2 3 3 


4 4 5 


83 


9191 


9196 


9201 


9206 


9212 


9217 


9222 


9227 


9232 


9238 


1 1 2 


2 3 3 


4 4 5 


84 


9243 
9294 


9248 


9253 


9258 


9263 


9269 


9274 


9279 


9284 


9289 


112 


2 3 3 


4 4 5 


85 


9299 


9304 


9309 


9315 


9320 


9325 


9330 


9335 


9340 


1 r 2 


2 3 3 


4 4 5 


86 


9345 


Q350 


9355 


9360 


93^5 


937o 


9375 


938o 


9385 


9390 


112 


2 3 3 


4 4 5 


87 


9395 


9400 


9405 


9410 


9415 


9420 


9425 


9430 9435 


9440 


Oil 


223 


3 4 4 


88 


9-145 


9450 


9455 


9460 


9465 


9469 


9474 


94 79 9484 


04 8q 


Oil 


223 


3 4 4 


89 


9494 


9499 


9504 


9509 


9513 


95i8 


9523 


9528 


9533 


9538 


Oil 


223 


3 4 4 


90 


9542 


9547 


9552 


9557 


9562 


9566 


9571 


9576 


958i 


9586 


Oil 


2 2,3 


3 4 4 


91 


9590 


9595 


9600 


9605 


9609 


9614 


9619 


9624 


9628 


9633 


Oil 


2 2 3 


3 4 4 


92 


9638 


9643 


9647 


9652 


9657 


9661 


9666 


9671 9675 


968c 


Oil 


223 


3 4 4 


93 


9685 


9689 


9694 


9699 


9703 


9708 


97*3 


9717 


9722 


9727 


Oil 


223 


3 4 4 


94 


9731 


9736 


9741 


9745 


9750 


9754 
9800 


9759 

9805 


97^3 
9809 


9768 


9773 


1 1] 2 2 3 


3 4 4 


95 


9777 


Q782 


9786 


9791 


Q795 


98 f4 


9818 


Oil 


223 


3 4 4 


96 


9823 


9827 


9832 


98 36 


9841 


9845 


9850 


9854 
9S99 


9359 


9863 


Oil 


223 


3 4 4 


97 


9868 


9872 


9877 


9881 


93F6 


9890 


9894 


9903 990S 
99489952 


Oil 


2 2 3 


3 4 4 


98 


9912 


9917 


9921 


9926 


9930 


9934 


9939 


9943 


I 1 


22^ 


3 4 4 


99 


99569961 996519969 


9974 


99789983 


9987 


9991I9996! 


Oil 


223 


3 3 4 



412 APPENDIX. 

Explanation of the Table for Finding the Area of 
Segment of a Circle. — The areas given in the table are for 
a circle I inch in diameter. The diameter is divided into 
iooo parts, and the area for segments of different heights can 
be taken directly from the table, since the ratio of the height 
of the segment to the diameter of the circle is the same as 
the height of the segment. 

For a circle whose diameter is other than unity. Given 
the diameter of the circle and the height of segment. Re- 
quired area of segment. Divide height of segment by diameter ; 
find area given in the table opposite this ratio ; multiply this 
area by the square of the diameter and the result is the re- 
quired area. 

Example. — Dia. of circle = 60", height of segment =18". 

18 -7- 60 = .30; area in table opposite .30 is . 19817. 
.19817 X 60 X 60 = area of segment = 713.4 sq. in. 

Given the diameter of the circle and the area of a segment, 
to find the height. 

Divide the area of the segment by the square of the diam- 
eter. Find in the table the area nearest to this, multiply 
the ratio corresponding to this by the diameter of the circle, 
and the result is the required height of the segment. 

Example. — Area of segment = 713.4 sq. in. 

Diameter of circle = 60" . Required the height of the 
segment. 

^ ' = .10817. Ratio opposite this is .300. 
60 X 60 v ' ^ 

.300 X 60" = 18", the required height. 

Example — Area of segment = 640 sq. in. 
Diameter of circle = 50" '. 

640 



.2560; nearest ratio, .362. 



50 X 50 

.362 X 50 = 18. 10", the required height. 



APPENDIX. 413 

TABLE FOR FINDING AREAS OF SEGMENTS OF A CIRCLE. 





tj <o 




*j 




«ou 


^ 


«o«J 




a v 




£i**T, 




•C "-"T, 


c 


•G ♦ J V. 


c 


•^ -"T. 


c 


-c -"r; 




b/o^ a 


<o 


JP-2 


u 


ta^ t 


V 


wi w a 


<o 


S°~" 


0) 


V Crj 

Kg" 


a 

be 
to 




S 
be 

V 

w 


<U Cm 

•*? bo . 


a 
be 

<L> 
C/5 


'53 Crj 

•*< a ■+-< 
fc* • 


S 
be 

<u 


-1° 


a 

be 
<u 

(73 


io 

Se ; 
iam, 





O rt 


*o 


O <u a 
O rt 




« a 
2^1 




<u a 


O 


SoQ 





'^oQ 




rtoQ 


(LI 


5 oQ 


a 


SoQ 


£2 


« 


< 


X 


<J 


Pi 


< 


05 


< 


rt 


«3 


.210 


.11990 


.260 


.16226 


.310 


.20738 


.360 


•25455 


.410 


•30319 


1 


.12071 


1 


.16314 


1 


.20830 


1 


•25551 


1 


•30417 


2 


.12T53 


2 


.16402 


2 


.20923 


2 


•25647 


2 


.305*6 


3 


.12235 


3 


.16490 


3 


.21015 


3 


•25743 


3 


.306/4 


4 


.12317 


4 


.16578 


4 


.21108 


4 


•25839 


4 


.30712 


.215 


.12399 


.265 


.16666 


•315 


.21201 


•365 


•25936 


•415 


.30811 


6 


.12481 


6 


•16755 


6 


.21294 


6 


.26032 


6 


.30910 


7 


.12563 


7 


.16843 


7 


.21387 


7 


.26128 


7 


.31008 


8 


.12646 


8 


.16932 


8 


.21480 


8 


.26225 


8 


.31107 


9 


.12729 


9 


. 1 7020 


9 


•21573 


' 9 


.26321 


9 


.31205 


.220 


.12811 


.270 


.17109 


.320 


.21667 


•37° 


.26418 


.420 


• 3*304 


1 


.12894 


1 


.17198 


1 


. 2 I 760 


1 


.26514 


1 


• 3M03 


2 


.12977 


2 


.17287 


2 


.21853 


2 


.26611 


2 


.31502 


3 


.13060 


3 


•17376 


3 


•21947 


3 


.26708 


3 


.31600 


4 


■13144 


4 


•17465 


4 


. 22040 


4 


,26805 


4 


.31699 


• 225 


.13227 


•275 


•17554 


.325 


.22134 


•375 


.26901 


•425 


.31798 


6 


•13311 


6 


.17644 


6 


.22228 


6 


.26998 


6 


•31897 


7 


•13395 


7 


•17733 


7 


.22322 


7 


.27095 


7 


.31996 


8 


•13478 


8 


.17823 


8 


.22415 


8 


.27192 


8 


•32095 


9 


•13562 


9 


.17912 


9 


.22509 


9 


.27289 


9 


.32194 


• 230 


.13646 


.280 


.18002 


•330 


.22603 


.380 


.27386 


•430 


.32293 


1 


.13731 


1 


.18092 


1 


.22697 


1 


•27483 


1 


.32392 


2 


.13815 


2 


.18182 


2 


.22792 


2 


.27580 


2 


.32491 


3 


.13900 


3 


.18272 


3 


.22886 


3 


.27678 


3 


•32590 


4 


• 13984 


4 


.18362 „ 


4 


.22980 


4 


•27775 


4 


.32689 


•235 


.14069 


.285 


.18452 


•335 


•23074 


.385 


.27872 


•435 


.32788 


6 


•14154 


6 


.18542 


6 


•23169 


6 


.27969 


6 


•32887 


7 


•M 2 39 


7 


.18633 


7 


.23263 


7 


.28067 


7 


•32987 


8 


•14324 


8 


.18723 


8 


•23358 


8 


.28164 


8 


•33086 


9 


.14409 


9 


.18814 


9 


■23453 


9 


.28262 


9 


•33185 


.240 


.14494 


.290 


.18905 


•34o 


•23547 


•39o 


•28359 


.440 


•33284 


1 


.14580 


1 


.18996 


1 


.23642 


1 


.28457 


' 1 


•33384 


2 


.14666 


2 


.19086 


2 


•23737 


2 


•28554 


2 


•33483 


3 


■14751 


3 


.19177 


3 


•23832 


3 


.28652 


3 


•33582 


4 


.14837 


4 


.19268 


4 


.23927 


4 


.28750 


4 


.33682 


•245 


.14923 


•295 


.19360 


•345 


.24022 


•395 


.28848 


•445 


•33781 


6 


.15009 


6 


.19451 


6 


.24117 


6 


■ 28945 


6 


.33880 


7 


•15095 


7 


.19542 


7 


.24212 


7 


.29043 


7 


•33980 


8 


.15182 


8 


•19634 


8 


.24307 


8 


.29141 


8 


•34079 


9 


.15268 


9 


•19725 


9 


.24403 


9 


.29239 


9 


.34179 


.250 


•15355 


.300 


.19817 


•350 


.24498 


.400 


•29337 


•450 


•34278 


1 


•15441 


1 


.19908 


1 


•24593 


1 


•29435 


1 


•34378 


2 


•15528 


2 


.20000 


2 


.24689 


2 


•29533 


2 


•34477 


3 


•15615 


3 


. 20092 


3 


.24784 


3 


.29631 


3 


•34577 


4 


.15702 


4 


.20184 


4 


.24880 


4 


.29729 


4 


.34676 


•255 


^5789 


■305 


.20276 


•355 


.24976 


.405 


.29827 


•455 


•34776 


6 


.15876 


6 


.20368 


6 


.25071 


6 


.29926 


6 


.34876 


7 


•15964 


7 


. 20460 


7 


•25167 


7 


. 30024 


7 


•34975 


8 


.16051 


8 


•20553 


8 


.25263 


8 


.30122 


8 


•35075 


9 


.16139 


9 


.20645 


9 


•25359 


9 


.30220 


9 


•35175 



414 



APPENDIX 



NATURAL TRIGONOMETRIC 
FUNCTIONS. 



CIRCLES 



Deg. 


Sine. 


Tangent. 


Cot. 


Cos. 

1. 0000 


Deg. 





.0000 


.OOOO 


Infinite 


90 


I 


OI75 


•0175 


57 290 


.9998 


89 


2 


•0349 


•0349 


28.636 


•9994 


88 


3 


•O523 


.0524 


19.081 


.9986 


87 


4 


.0698 


.0699 


14.301 


.9976 


86 


5 


.0872 


.0875 


11.430 


.9962 


85 


6 


.IO45 


.1051 


9-51-14 


•9945 


84 


7 


.1219 


.1228 


8.1443 


.9925 


83 


8 


.1392 


.1405 


7.II54 


•9903 


82 


9 


.1564 


.1584 


6.3138 


, 9 S 7 7 


81 


IO 


.1736 


.1763 


5.6713 


.9848 


80 


ii 


.1908 


.1944 


5.1446 


.9816 


79 


12 


.2079 


.2126 


4.7046 


.9781 


78 


13 


.2250 


.2309 


4.3315 


• 9744 


77 


14 


.2419 


•2493 


4.0108 


•9/03 


76 


15 


.2588 


.2679 


3.7321 


.9659 


75 


16 


.2756 


.2867 


3.4874 


.9613 


74 


17 


.2924 


•3057 


3.2709 


.9563 


73 


18 


.3090 


.3249 


3.0777 


• 95ii 


72 


19 


•3256 


• 3443 


2.9042 


•9455 


71 


20 


.3420 


.3640 


2-7475 


•9397 


70 


21 


.3584 


•3839 


2.6051 


.9336 


69 


22 


•3746 


.4040 


2-4751 


.9272 


68 


23 


•3907 


.4245 


2-3559 


.9205 


67 


24 


.4067 


•4452 


2.2460 


• 9*35 


66 


25 


.4226 


.4663 


2.1445 


.9063 


65 


26 


•4384 


•4877 


2.0503 


.8988 


64 


27 


•4540 


.5095 


1.9626 


.8910 


63 


28 


.4095 


.5317 


1.8807 


.8829 


62 


29 


.4848 


• 5543 


1 . 8040 


.8746 


61 


30 


.5000 


• 5774 


1.7321 


.8660 


60 


31 


.5150 


.6009 


1.6643 


.8572 


59 


32 


.5299 


.6249 


1 . 6003 


.8480 


58 


33 


•5446 


.6494 


1-5399 


.8387 


57 


34 


•559 2 


•6745 


14826 


.8290 


56 


35 


•5736 


.7002 


i.428r 


.8192 


55 


36 


.5878 


.7265 


1.3764 


.8090 


54 


37 


.6018 


•7536 


1.3270 


.7986 


53 


38 


.6157 


.7813 


1.2799 


.7880 


52 


39 


.6293 


.8098 


1.2349 


•7771 


5i 


40 


.6428 


•8391 


1.191S 


.7660 


50 


4i 


.6561 


.8693 


1. 1504 


•7547 


49 


42 


.6691 


.9004 


1. 1 106 


•743i 


48 


43 


.6820 


•9325 


1.0724 


.7314 


47 


44 


.6947 


.9657 


1.0355 


•7193 


46 


45 


.7071 


1. 0000 


1. 0000 


.7071 

Sine. 


45 


Deg. 


Ccs. 


Cot. 


Tangent. 


Deg. 



Diam. 


Circumf. 


Area, 


Inches. 


Inches. 


Sq. In. 


12 


37l 


H3| 


14 


44 


154 


16 


50i 


201 


18 


sH 


254* 


20 


62| 


3Hh 


22 


69i 


3 hol 


24 


751 


452| 


26 


Sif 


53i 


28 


88 


61 =f 


30 


94^ 


7 c6| 


32 


icoi 


So 4 i 


34 


1 06! 


. 907| 


36 


"Si 


1017I 


38 


*i9f 


i j 34f 


40 


!25f 


1256! 


42 


I32 


I 3S5^ 


44 


I38| 


i<;2oi 


46 


1 44* 


i66i| 


48 


I 50| 


1809I 


50 


I57i 


1963* 


52 


i6 3 f 


2123I 


54 


i6 9 i 


22903- 


56 


i75| 


2463 


58 


182^ 


2642J 


60 


i88i 


2827! 


62 


i 9 4f 


3019^ 


64 


201 


3217 


66 


207I 


342ii 


68 


213I 


563if 


70 


2J9f 


3848^ 


72 


2261 


4071I 


74 


2 3 2i 


43CO| 
4536J 


76 


2 3 8f 


78 


245 


4778| 


80 


25if 


5026! 


82 


257i 


5281 


84 


263! 


554if 


86 


2701 


5 8o8| 


88 


2 7 6i 


6oS2£ 


90 


282I 


6 3 6if 


92 


289 


6647I 


94 


295! 


69391 


96 


301$ 


72 3 8* 


98 


307! 


7543 


100 


314* 


7854 


102 


320f 


8171* 



APPENDIX. 
ROUND RODS OF WROUGHT IRON. 



415 



Diameter 
in Inches-. 



1/16 

1/8 

3/16 

1/4 

5/16 

3/8 

7/16 

1/2 

9/16 

5/8 

11/16 

3/4 
13/16 

7/8 
15/16 



1/16 

1/8 

3/i6 

1/4 
5/16 
3/8 
7/16 



Circumfer- 
ence 

in Inches. 



1/2 

5/8 
3/4 
7/8 



1/8 

1/4 
3/8 

1/2 
5/8 
3/4 
7/8 



.1963 
.3927 
•5890 

.7854 

.9817 

1.1781 

1-3744 

1.5708 
1. 7671 
1.9635 
2.1598 

2.3562 

2.5525 
2.7489 
2.9452 

3.1416 
3-3379 
3-5343 
3.7306 

3.9 2 7o 
4-1233 

4.3I97 
4.5160 

4.7124 
5.1051 
5.4978 
5.8905 

6.2832 
6.6759 
7.0686 
7-4613 

7.8540 
8.2467 
8.6394 
9.0321 

9.4248 



Area in 
Sq. Inches. 



.OO31 
.0123 
.0276 

.0491 
.0767 
.IIO4 

•1503 

.1963 

.2485 
.3068 
•3712 

.4418 
.5185 
.6013 
.6903 

.7854 

.8866 

•9940 

1. 1075 

1.2272 
I.3530 
1.4849 
1.6230 

1. 7671 
2.0739 

2.4053 
2.7612 

3.1416 

3.5466 
3.9761 
4.4301 

4.9087 
5.4II9 

5.9396 
6.4918 

7.0686 



Weight 


Diameter 


Diameter 




of Rod 


of Upset 


of Screw 


Threads 


One Foot 


Screw 


at Root of 


per Inch. 


Long. 


End. 


Thread. 


Number. 




Inches. 


Inches. 




.010 








.041 








.O92 








.164 








.256 








.368 








.501 








.654 


t 


.620 


IO 


.828 


1 


.620 


IO 


1.023 


7 

8 


•731 


9 


I.237 


I 


.837 


8 


1-473 




.837 


8 


I.728 


I* 


.940 


7 


2.OO4 


1* 


I.065 


7 


2.3OI 


T l 


I.065 


7 


2.6l8 


If 


1. 160 


6 


2-955 


If 


1. 160 


6 


3.313 


I* 


I.284 


6 


3.692 


T l 


I.284 


6 


4.O9I 


If 


I.389 


5» 


4.5IO 


If 


I.490 


5 


4-950 


T 3 


I.490 


5 


5.4IO 


If 


1. 615 


5 


5.89O 


2 


I. 712 


4* 


6.913 


H 


1.837 


4* 


8.OI8 


2i 


1 . 962 


4* 


9.204 


2f 


2.087 


4* 


I0.47 


"* 


2.175 


4 


11.82 


H 


2.300 


4 


13-25 


2| 


2.550 


4 


14-77 


3 


2.629 


3* 


16.36 


31 


2.754 


3h 


18.04 


3i 


2.879 


Sk 


19.80 


3f 


3.OO4 


3h 


21.64 


31 


3.225 


3i 


23.56 


3f 


3.317 


3 



Excess of 
Effective 
Area of 
ScrewEnd 
over Bar. 
Per Cent. 



57 
4* 

25 
34 
48 
29 

35 
19 
30 
17 

23 
29 
18 
26 

30 
28 
26 
24 

18 
17 
28 

23 

21 
20 

19 
26 

22 



4i6 



APPENDIX. 
LAP-WELDED BOILER-TUBES. 





iT 


s-T 


t/i 


X 


c 


<Z 12 


w"_j 


.** x 


** C 


. , 


*j V. 






w 


V 


2 


w^ 




v c 


Si rt 


fcW 


fc~ 


£ « 


&H a 


j 


v 


a 

5 

11 


a 

S _ 
ex: 

'- u 
U G 


I 

en 
U 

C 

5 


, en 

CD eu 
oX! 

c °. 

euJ3 


,"en 

OX! 

c a 

<U C 

4J — ' 

Is 


X 

u r 
to 

s ^ 


<£ 

HI 

c 

CO 

b' 


m <u 

XC/3 rt 

to E 

So* 


& - 

to E 
c ^ 


a xf 
ti 

C/2 


c 

to 

c 

„-« 

m 


O 

£ 

u 


a 

XI 

to 


c75 


w 


1-1 


H 


u 


U 


H 


H 


1-3 


J 


£ 


i 


! 


.86 


.072 


3-M 


2.69 


.78 


•57 


3-82 


4.46 


.26 


.22 


•71 


Wa 


lJ4 


i. ii 


.072 


3-93 


3-47 


1.23 


.96 


3 


06 


3-45 


•33 


.29 


.89 


jH 


1^ 


i-33 


.083 


4.71 


4.19 


1.77 


1.40 


2 


55 


2.86 


•39 


•35 


1.24 


i% 


1% 


1.56 


•095 


5-50 


4.90 


2.40 


1. 91 


2 


18 


2-45 


.46 


.41 


1.66 


2 


2 


1. 81 


•095 


6.28 


5-69 


3.14 


2-57 


1 


9i 


2. 11 


•52 


•47 


1. 91 


2J4 


2*4 


2.06 


•095 


7.07 


6.47 


3.98 


3-33 


1 


70 


1.85 


•59 


•54 


2.16 


2^ 
2% 


2^ 


2.?8 


.109 


7-85 


7.17 


4.91 


4.09 


1 


53 


1.67 


.65 


.60 


275 


2% 


2-53 


.109 


8.64 


7-95 


5-94 


5 -03 


1 


39 


i-5i 


•72 


.66 


3 -°4 


s 


3 


2.78 


.109 


9.42 


8.74 


7.07 


6.08 


1 


27 


i-37 


•79 


•73 


3-33 


i 


3M 


301 


. 120 


10.21 


9.46 


8.30 


7.12 


1 


17 


1.26 


.85 


•79 


3-96 


3*1 


3.26 


.120 


11.00 


10 24 


9.62 


8-35 


i 


09 


1. 17 


.92 


•85 


4.28 


3% 


3% 


3-5i 


.120 


11.78 


11.03 


11 .04 


9.68 


1 


02 


1.09 


.98 


.Q2 


4.60 


4 f . 


4 


3-73 


.134 


12-57 


11.72 


12.57 


IO. Q4 




95 


1 .02 


i-°5 


.98 


5-47 


4^ 


aM 


4.23 


■134 


14.14 


13.29 


15.90 


14.07 




85 


.90 


1. 18 


I. II 


6.i 7 


5 


5 


4.70 


.148 


I5-7I 


14.78 


19.63 


17.38 




76 


.81 


1 -3i 


1.23 


7.58 


6 


6 


5-6 7 


.165 


18.85 


17.81 


28.27 


25.25 




64 


.67 


i-57 


I.48 


10.16 


7 


7 


6.67 


.165 


21.99 


20.95 


38.48 


34-94 




55 


•57 


1.83 


!-75 


11.90 


8 


8 


7.67 


.165 


25-13 


24.10 


50.27 


46.20 




48 


•5° 


2.09 


2.01 


i3-o5 


9 


9 


8.64 


.180 


28.27 


27.14 


63.62 


58.63 




42 


•44 


2-35 


2.26 


16.76 


IO 


IO 


9-59 


• 203 


3I-42 


30.14 


78.54 


72.29 




38 


.40 


2.62 


2.51 


20.09 


n 


II 


10.56 


.220 


34-56 


33-17 


95-03 


87.58 




35 


•36 


2.88 


2.76 


25-03 


12 


12 


"54 


.229 


37-7° 


36.26 


113. IO 


104.63 




32 


•33 


3-*4 


3.02 


28.46 



SCREW-THREADS. 

Angle of thread 6o°. Flat at top and bottom = ^ of pitch. 



Diameter of 


Diameter at 


Threads 


Diameter of 


Diameter at 


Threads 


Screw, 


Root of Thread, 


per Inch, 


Screw, 


Root of Thread, 


per Inch, 


Inches. 


Inches. 


No. 


Inches. 


Inches. 


No. 


Ya 


.185 


20 


2 


1. 712 


4^ 


ft 


.240 


18 


2M 


1. 962 


4H 


% 


.294 


16 


2M 


2.^75 


4 


iz 


•344 


14 


2.425 


4 


% 


.400 


13 


\, 


2.629 


3H 


ft 


•454 
•507 


12 
11 


% 


2.879 
3.100 


&$ 

M 


ft 


.620 


10 


M 


3-3'7 


3 


% 


•73i 


9 














4 


3-5°7 


3„, 


I 


.837 


8 


4 H 


3-798 


2 % 


1^ 


.940 
1.065 


7 
7 


g 


4.028 
4-255 


ft 


*% 


1. 160 


6 














5 


4.480 


*\b 


\\4> 


1.284 


6 


1 


4-73Q 


2^ 


1% 


I-389 


5Y2 


5-OS3 


2% 


%. 


1.490 


5 


sM 


5-203 


2% 


1% 


1. 615 


5 


6 


5-423 


2J4 



APPENDIX. 417 

WROUGHT-IRON WELDED STEAM-, GAS-, AND WATER-PIPE. 





Diameter. 






Transverse Areas. 


Nominal 


Number of 








Thickness. 






Weight 

per 

Foot. 


Threads 
per Inch of 


Nominal 


Actual 


Actual 


External. 


Internal. 


Internal 


External. 


Internal. 












Inches. 


Inches. 


Inches. 


Inches. 


Sq. In. 


Sq. In. 


Pounds. 




8 


.405 


.27 


.068 


.129 


•o573 


.241 


27 


ft 


•543 


■364 


.088 


.229 


.1041 


.42 


18 


•675 


•494 


.091 


.358 


.1917 


•559 


18 


-* 


.84 


.623 


.109 


•554 


.3048 


•837 


14 


1.05 


.824 


•"3 


.866 


•5333 


1. 115 


14 




i-3iS 


•1 .048 


•134 


1.358 


.8626 


1.668 


»*£ 


"M 


1.66 


1.38 


.14 


2.164 


1.496 


2.244 


"^ 


i}| 


1.9 


1.6x1 


•MS 


2.835 


2.038 


2.678 


"fc& 


2 


2-375 


2.067 


-154 


4-43 


3.356 


3-609 


2^ 


2.875 


2.468 


.204 


6.492 


4-784 


5-739 


8 


3 W 


3-5 


3.067 


.217 


9.621 


7.388 


7-536 


8 


3^ 


4- 


3-548 


.226 


12.566 


9.8S7 


9.001 


8 


4 


4-5 


4.026 


-237 


15.904 


12.73 


10.665 


8 


4^ 


5- 


4.508 


.246 


I9-635 


15.961 


12.34 


8 


5 


5-563 


5-045 


•259 


24 . 306 


19.99 


14.502 


8 


6 


6.625 


6.065 


.28 


34-472 


28.888 


18.762 


8 


7 


7.625 


7.023 


.301 


45.664 


38.738 


23.271 


8 


8 


8.625 


7.982 


.322 


58.426 


50.04 


28.177 


8 


9 


9.625 


8-937 


•344 


72.76 


62.73 


33-7oi 


8 


10 


i».75 


10.019 


.366 


90.763 


78.839 


40.065 


8 


11 


12 


11.25 


-375 


113.098 


99.402 


45-95 


8 


12 


I2 -75 


12 


•375 


127.677 


113.098 


48.985 


8 


*3 


14 


13-25 


•375 


153.938 


137.887 


53-921 


8 


14 


15 


14.25 


•375 


176.715 


159-485 


57-893 


8 


15 


16 


15-25 


•375 


201 .062 


182 655 


61.77 


8 




18 
20 
22 
24 


1725 
19-25 
21.25 
23.25 


•375 
•375 
•375 
•375 


254-47 
314.16 
380.134 
452-39 


233.706 
291.04 
354 657 
424.558 


69.66 
77-57 
85.47 
93-37 





















WROUGHT-IRON WELDED EXTRA STRONG PIPE. 



% 


.405 


.205 


.1 


.129 


•033 


.29 


27 


Ya 


•54 


.294 


.123 


.229 


.068 


•54 


18 


% 


•675 


.421 


.127 


.358 


•139 


•74 


18 


/^ 


.84 


•542 


.149 


•554 


.231 


1.09 


14 


n 


1.05 


•736 


•157 


.866 


•452 


1-39 


14 


i 


1. 3i5 


•951 


.182 


1-358 


•7i 


2.17 


11^ 


iJ4 


1.66 


1.272 


.194 


2.164 


1. 271 


3 


ii^j 


*\6 


1.9 


1.494 


.203 


2.835 


1-753 


3-6 3 


IlJ^S 


2 


2-375 


1-933 


.221 


4-43 


2-935 


5.02 


1114 


2^ 


2.875 


2-315 


.28 


6.492 


4.209 


7.67 


8 


3 


3-5 


2.892 


•304 


9.621 


6.569 


10.25 


8 


3H 


4 


3-358 


.321 


12.566 


8.856 


12.47 


8 


4 


4-5^ 


3.818 


-341 


I5-904 


11.449 


14.97 


8 


5 


5563 
6.625 


4.813 


•375 


24.306 


18.193 


20.54 


8 


6 


5-75 


•437 


34.472 


25.967 


28.58 


8 



4i8 



APPENDIX. 



HEAT OF THE LIQUID. 



fa 


' 
— n 


fa 





fa* 





fa 


CJ 


^ 


' 

n 


fa 





o 


tr-- « 





*:§• 





««:2« 


O 


■m3 » 





<-:- a; 





«*<"0 oj 




C 3 > 




C 3 > 




C 3 > 




O 3 > 




C 3 > 




°'B £ ' 


ft 


+> ?o 


ft 


-* ^S 


ft 


■*» o"8 


ft 


+- Cg 


ft 


~ ~~ 


ft 


~ & 2 


s 

03 


OS ►— 1 c3 


0! 




s 

03 


4>fa 03 


03 


031-1 CJ 


a 

33 


03 1-1 rt 


i 


03---2 


H 


X 
0.0 


~7 


X 


H 


X 


H 


X 


Eh 


X 


£ 


X 


V 


44.1 


121 


89.O 


166 


1340 


211 


179.3 


256 


224.9 


33 


I 





77 


45-1 


122 


90.0 


167 


1350 


212 


180.3 


257 


225.9 


34 


2 





78 


46 . 1 


123 


91 .O 


168 


136.0 


213 


181. 3 


258 


226.9 


35 


3 





79 


47 .1 


124 


92 .O 


169 


137.0 


214 


182.3 


259 


227.9 


36 


4 





80 


48.1 


125 


93 


I70 


138.0 


2I 5 


183.3 


260 


229.0 


37 


5 





81 


49- 1 


126 


94.0 


171 


139.0 


2l6 


184.3 


261 


230.0 


38 


6 


1 


82 


50.1 


127 


95° 


172 


140.0 


217 


185.3 


262 


231 


39 


7 


1 


83 


5ii 


128 


96.0 


173 


141 .0 


2T.8 


186.3 


263 


232 .0 


40 


8 


1 


84 


52.1 


129 


97.0 


174 


142 .0 


219 


187.4 


264 


2330 


41 


9 


1 


85 


53.1 


130 


98.0 


175 


143 -o 


220 


188.4 


265 


234 


42 


10 


1 


86 


54.1 


131 


99 


176 


144.0 


221 


189.4 


266 


2350 


43 


11 


1 


87 


55- 1 


132 


100 .0 


177 


I45-0 


222 


190.4 


267 


236.1 


44 


12 


1 


88 


56.1 


133 


101 .0 


178 


146 .0 


223 


191. 4 


268 


237.1 


45 


13 


1 


89 


57-1 


134 


102 .0 


179 


147.0 


224 


192.4 


269 


238.1 


46 


14 


1 


90 


58.1 


135 


103.0 


180 


148 .0 


225 


193-4 


270 


230. 1 


47 


15 


1 


91 


59-1 


136 


104.0 


181 


1490 


226 


1944 


271 


240. 2 


48 


16 


1 


92 


60. 1 


1.3 7 


105.0 


182 


150 . i 


227 


195 4 


272 


2-.I . 2 


49 


17 


1 


93 


61. 1 


138 


106 .0 


183 


151-1 


228 


196.5 


273 


242.2 • 


50 


18 


1 


94 


62 . 1 


139 


107.0 j 


184 


152 .1 


229 


197.5 


274 


243-2 


51 


19 


1 


95 


63.1 


140 


108.0 


185 


153. 1 


230 


198.5 


275 


244.2 


52 


20 


1 


96 


64. 1 


141 


109 .0 


186 


154. 1 


231 


199 -5 


276 


245-3 


53 


21 


1 


97 


65.0 


142 


IIO.O 


187 


I55-I 


232 


200. 5 


277 


246.3 


54 


22 


1 


98 


66.0 


143 


III .0 


188 


156. 1 ! 


233 


20T . 5 


278 


247-3 


55 


23 


I 


99 


67 .0 


144 


112 .O 1 


189 


157. 1 


234 


202 . 5 


279 


248.3 


56 


24 


1 


100 


68.0 


145 


113 .O 


190 


158. 1 


235 


203 .6 


280 


249-4 


57 


25 


1 


101 


69 .0 


146 


114. O 


191 


159. 1 


236 


204 .6 


281 


. 250.4 


58 


26 


I 


102 


70 .0 


147 


115 .O 


192 


160 . 1 


237 


205.6 


282 


251-4 


59 


27 


1 


103 


71 .0 


148 


Il6. O 


193 


161. 1 


238 


206.6 


283 


252.4 


60 


28 


1 


104 


72 .0 


149 


117 .O 


194 


162 . 1 


239 


207 . 6 


284 


2 53-4 


61 


29 


1 


105 


73-0 


150 


Il8. O 


195 


163 .1 


24O 


208.6 


285 


254.5 


62 


30 


1 


106 


74.o 


151 


IIQ .O 


196 


164 . 1 


241 


209 . 6 


286 


2555 


63 


3i 


1 


107 


75-0 


152 


I20.0 


197 


165 . 1 


242 


210. 7 


287 


256.5 


64 


32 


1 


108 


76 .0 


153 


121 .O 


198 


166.2 


243 


211 . 7 


288 


257.5 


65 


33 


1 


109 


77-0 


i54 


122 .O 


199 


167 . 2 


244 


212.7 


289 


258.6 


66 


34 


1 


no 


78.0 


i55 


123 .O 


200 


168.2 


245 


2137 


290 


259.6 


67 


35 


1 


III 


790 


156 


I24.O 


201 


169. 2 


246 


214.7 


291 


260.6 


68 


36 


1 


112 


80.0 


i57 


125 .O 


202 


170 . 2 


247 


215 7 


292 


261 .6 


69 


37 


1 


113 


81 .0 


158 


126 .O 


203 


171 .2 


248 


216.7 


293 


262 .7 


70 


38 


1 


114 


82.0 


i59 


I27.0 


204 


172 .2 


249 


217.7 


294 


263.7 


7i 


39 


1 


115 


830 


160 


I28.O 


205 


173.2 


250 


218.8 


295 


264.7 


72 


40 


1 


Il6 


84.0 


161 


129 .O 


206 


174.2 


251 


219.8 


296 


265.7 


73 


41 


1 


117 


85.0 


162 


I30.0 


207 


1752 


252 


220.8 


297 


266.7 


74 


42 


1 


Il8 


86.0 


163 


131 O 


208 


176 . 2 


253 


221 .8 


298 


267 8 


75 


43 


1 


119 


87.0 


164 


132 .O 


209 


177.2 


254 


222 .8 


299 


268.8 






I20 


88.0 


165 


I33-0 


210 


178.3 


255 


223.8 


300 


269.8 



VOLUME AND WEIGHT OF DISTILLED WATER. 



Temp. 


Weight of a 


Temp 


Weight of a 


Temp. 


Weight of a 


Degrees 


Cubic Foot 1 


Degrees 


Cubic Foot 


Degrees 


CuHc Foot 


Fahr. 


in Pounds. 


Fahr. 


in Pounds. 


Fahr. 


in Pounds. 


32 


62 .417 


90 


62.110 


160 


61 .007 


39- 1 


62 . 425 


100 


62 . 000 


1 7c 


60.801 


40 


62.423 J 


I lO 


61.867 


180 


60. 587 


50 


62 . 409 


120 


61 . 720 


190 


60.366 


60 


62 .367 


130 


61.556 


200 


60. 136 


70 


62 .302 


140 


61.388 


210 


59 894 


80 


62 .218 


150 


61 . 204 


212 


59- 707 



APPENDIX. 



419 





PROPERTIES OF 


SATURATED STEAM. 




Pressure 
Pounds 


Temp, at 


Heat of 


Total Latent 
Heat 


Total Heat 


Volume in 

Cubic Feet 

0' 


Absolute 


Vaporization, 


Liquid 


or Heat of 


above Water 


on Square 
Inches. 


Degrees F. 


above 32 . 


Vaporization. 


at 32 F. 


One Pound. 


5 


162.3 


*3°-3 


IOOI. 2 


"3"5 


73-38 


10 


193.2 


161 .4 


979-5 


1140.9 


38-25 


15 


213.0 


181. 3 


965.6 


1146.9 


26. 20 


20 


227.9 


196.5 


955-o 


"5"5 


19-95 


25 


240.0 


208.7 


946.4 


"55-1 


16.16 


3° 


250.3 


219. 1 


939-2 


«S8-3 


13.62 


35 


259.2 


228.1 


932-9 


1161 .0 


11.77 


40 


267.1 


236.2 


927.2 


1163.4 


10.39 


45 


274-3 


243-5 


922. 1 


1165.6 


9-304 


5° 


280.8 


250.2 


917.4 


1167.6 


8.429 


55 


286.9 


256-4 


913.0 


1169.4 


7-709 


60 


292.5 


262.1 


909.1 


1171.2 


7.107 


65 


297.8 


267-5 


905-2 


1172.7 


6.592 


70 


302.7 


272.6 


901.7 


"74-3 


6. 151 


75 


3°7-4 


277.4 


898.3 


"75-7 


5-769 


80 


311. 8 


281.9 


895.1 


1177.0 


5-431 


85 


316.0 


286.2 


892.1 


1178.3 


5-i3i 


90 


320.0 


290.3 


889-3 


1179.6 


4.864 


95 


323-9 


294-3 


886.4 


1180.7 


4.625 


100 


327.6 


298.1 


883.8 


1181.9 


4-409 


105 


33*-i 


301.8 


881. 1 


1182.9 


4. 212 


no 


334-6 


3°5-3 


878.7 


1184.0 


4-032 


ii5 


337-9 


308.8 


876.2 


1185.0 


3.868 


120 


341.0 


312.0 


874.0 


1186.0 


3-717 


125 


344- 1 


3i5-i 


871.8 


1186.9 


3-578 


130 


347- 1 


318.3 


869.5 


1187.8 


3-45o 


135 


35°-° 


321.3 


867.4 


1188.7 


3-329 


140 


352-9 


324.2 


865.3 


1189.5 


3.218 


145 


355-6 


327.0 


863.4 


1190.4 


3-^3 


150 


358-3 


329.8 


861.4 


1191. 2 


3.016 


155 


360.9 


33 2 -4 


859.6 


1192.0 


2.924 


160 


363-4 


335-1 


857.7 


1192.8 


2.838 


165 


365-9 


337-7 


855-9 


1193.6 


2.756 


170 


368 3 


340.2 


854.1 


"94-3 


2.681 


175 


37°-7 


342.6 


852.4 


1195.0 


2.608 


180 


373° 


344-9 


850.8 


"95-7 


2.540 


i85 


375-2 


347-4 


849.0 


1196.4 


2-475 


190 


377-4 


349-7 


847.4 


"97" 


2.413 


195 


379-6 


35i-9 


845.8 


"97 7 


2-355 


200 


381.7 


354-1 


844-3 


1198.4 


2. 299 


205 


383-8 


356-3 


842.7 


1199.0 


2. 246 


210 


385-9 


358.4 


841.2 


1199.6 


2"95 


215 


387-9 


360.5 


839-7 


1200. 2 


2.147 


220 


389-8 


362.5 


838 3 


1200.8 


2. IOI 


225 


391.8 


364.5 


836.9 


1201.4 


2.056 


230 


393-7 


366.6 


835.4 


1202.0 


2.013 


235 


395-6 


368.4 


834.2 


1202.6 


1.972 


240 


397-4 


370-4 


832.7 


1 203 . 1 


1.932 


245 


399-2 


372.2 


831.5 


1203.7 


1.895 


250 


401 .0 


374-1 


830.1 


1204.2 


1.858 



PLATE L 




PLATE II. 




F1C. 5 



FIG. 6 



PLATE II. 




PLATE IIL 




^SIDE LINER ^""THICK ^RIVETS 

|e 57%-- 

|i 28iVis- >k— - 

rk - .^ ij iiiii H ii h i j i w g »¥Wf i 



2SIi/is- 




"2, l ^"pLUGSe,AND F. 

E.78" F. 110%'VrOM BACK END, 



PLUG back Er;D 



2% PLUG FRONT END 



I THROUGH FIRE BOX REAR ELEVATION 



LOCOMOTIVE BOILER 

160 LBS. PRESSURE 



PLATE III. 



L_ 

----- 




-SONT HEAD. SECTION AT X.Y. 
T0TUB£S-2"OUT.SIDE DIAM. 



LUG FRONT END 



SECTION THROUGH FIRE BOX REAR ELEVATION 



PLATE IV, 




SECTION C-C LOOKING BACK 



(r. 








Qoooo 

aea. 



- 10 m — 

SECTION A-A LOOKING FRONT. 







SECTION B-B LOOKING FRONT. 



^ 



>£>^ 



I 



■ 



FAGE 


5, 3 26 


. 81 


5-227 


58,61 


. 61 


- 7i 


- 63 


•- 35i 


•■ 35 


-- 44 


.. 119 


•- 253 


•- 47 


-- 4i4 


-■ 297 


-- 379 


12, 413 


.. 6 


.. 6 


-- 318 


-- 59 


■- 55 


■- 38 


-- 38 


22 


•-- 275 


.-- 358 


. .. 28 



- 




t~HHH~ri^it-HMHH^-H-i-H 




INDEX. 



119 



PAGE 

■7 o C 2 26 

Accumulators ^ 3 ' J 

Acetic acid 

Adamson joints 22 5 22 ' 

Air for combustion 5 > 

dilution 

loss from excess ' 

per pound of coal 3 

supply for boiler, measurement of 35 1 

AI:ny boiler ; °3 

American independently-fired superheaters 

stoker 

2 ^ 3 
Angle- valves - °° 

Anthracite coal 4 ' 

Area of circles 

. 207 
steam-pipe v ' 

uptake 379 

Areas of segments of circles 4* 2 > 4*3 

Ash-pit 

doors 

Assembling and riveting boilers 3 l8 

Atmosphere, composition of 59 

Atomic weight 55 

Attached superheaters 3 8 

Babcock & Wilcox attached superheater 3 8 

boiler . . 22 

Baird's steam-trap 2 ?5 

Balancing heat in boiler test 35 

Belleville boiler 28 

Belpaire fire-box 2 ° 

421 



422 INDEX. 

PAGE 

Berryman feed-water heater 283 

Bituminous coal 48 

Blow-off pipes 286 

Blowing out brine 98 

Blue heat 190 

Board of Trade, rules for flues 235 

Boiler, foundation for 101 

selection of type of 360 

settings for B. & W 105 

Dutch oven •. m 

cylindrical tubular 102 

Heine 106 

marine water-tube .107 

Stirling 106 

Boilers, two-flue 6 

vertical 10-14 

water-tube 20 

marine 27 

Yarrow 32 

Boiler accessories 52 

design 360 

explosions 245 

front 6 

horse-power 1 48 

shop plan and description of 305 

testing, evaporative 7,7,^ 

tubes, size and surface of 416 

Boring-mill 3 t t 

Brackets 173, 391 

Brass - - 193 

Bridge-wall 2 

Brine, loss from blowing out 98 

Bronze 193 

Buck-staves 105 

Bumped up head 198 

Bundy steam-trap 277 

Bursting pressure of fittings 295 

Butt-joint - 202, 214, 216 

Calculation of gas analysis 67 

riveted joints 201 

stay-rods 385 

Calking 331 

Calorimeters for steam, Carpenter 345 

Peabody 342 






INDEX. 423 

PAGE 

Cam and toggle riveting-machine 321 

Carbon, heat of combustion of 53, 54 

Carbonate of lime 78 

Cast iron 191 

Chapman valves 254 

Channel-bars, calculation of 386 

Charcoal 49 

Check-valves 256 

Chemistry of combustion 54 

Chimney, area of 136 

draught 134 

forms of 136 

stability of 138 

Chimneys 132 

Kent's table 133 

Circles, area of 414 

circumference of 414 

Circumference of circles 414 

Cleaning fires 1 28 

Coal, air per pound of , 63 

conveyer 302 

belt 302 

bucket 301 

bucket-filler 302 

distributor 302 

value of 144 

volume of ton of 74 

Coals, anthracite 47 

bituminous 48 

caking, bituminous 48 

dry bituminous 48 

long-flaming bituminous . 48 

semi-bituminous 47 

Cold-water test • 332 

Collapsing pressure 223 

Coke 48 

Combination 266 

Combustion, air required for 58 

chemistry of . . . 54 

heat of 5°-5 2 > 5 6 

incomplete 70 

rate of 149 

temperature of 73 

volume of air for 61 

Complex stays 169 



424 INDEX. 

PAGE 

Composition 193 

of atmosphere 59 

of ^els . 50, 51, 52 

Compression 183 

Conical through tubes 8 

Copper 192 

Cornish boiler 8 

Corrosion 94 

Corrugated furnace 227 

Covering pipes, saving by . 299 

Crane-lifts 309 

Crown-bars 19 

Crowfeet 157 

Crushing of plate 204 

rivet 204 

Curtis separator .' 280 

steam-trap 277 

Cylinder, end tension in 196 

rim tension in 197 

strength of . . 196 

Cylindrical tubular boiler 2 

setting 102 

staying of 154 

Damper regulator 272 

Density of gases 55 

Detachable brackets 1 74 

Detroit separator 280 

Diagram for setting return tubular boilers 399 

Diameter of boiler . . 364 

rivet 205 

Diagonal stays 195 

Down-draught furnaces . 1 23 

Draught of chimneys 134 

forced and induced 125 

gauge 349 

Howdens system 127 

split 10 

wheel 9 

Drill for tube holes 310 

Drilled or punched plates .' 203 

Dry-pipe 171 

Du Long's formula 157 

Dudgeon tube-expander 329 



INDEX. 425 

PAGE 

Economizers , 1 29 

sizes of Green's 407 

of Sturtevant's 408, 409 

Efficiency of riveted joints 201 

Elasticity, modulus of 182 

Elastic limit 182 

Equivalent evaporation 146 

Evaporative test of boiler 352 

Excess of air, loss from 71 

Expanders for tubes 3.28, 3 29 

Expansion pads 20 

Explosions of boilers 245 

Factor of safety ._ 240, 366 

Farnley furnace 228 

Feed-pipes 283 

pumps 284 

water filter 87, 281 

Feed-water heaters (lime-extracting) 82 

Berryman 283 

Hoppes 82 

Wainwright 282 

impurities in (table) 76 

organic impurities 91 

Filter, feed-water 87, 281 

oil 281 

Finishing flanges 311 

Fire cracks 127 

doors '. 5 

engine boiler ."...."' 14 

tubes r 236 

Firing 115 

Fittings, bursting pressure of 295 

for superheated steam 46 

Flange-punch 309 

Flanging heads 307 

Flat plates 238 

Flow of steam 298, 347 

Flue-gases 348 

Flues 221 

area of 136 

collapsing, pressure of 223-235 

discussion of tests 233 

rules for 234 

strengthened 224 



426 INDEX. 

PAG-E 

Flynn stea-m-trap 276 

Forced draught 125 

Forms of test-pieces 179, 186 

Foster's independently-fired superheater 43 

Foundation for boilers 101 

Foundation ring 10 

Fox's corrugated furnace 227 

Friction of riveted joints 204 

Fuel, artificial 49 

standard 143 

Fuels, composition of 50, 51, 52 

Furnace, corrugated 227-233 

Dutch oven 43, 101 

Farnley's 228 

flues, tests of 223 

Hawley down-draught 1 24 

Holmes' 229 

Morison's 23 2 

mouth 167 

Purve's 232 

Furnaces 107 

down-draught 1 23 

oil-burning 1 24 

Fusible plugs 270 

Galvanic action 87 

Gas analysis, calculation of 67 

apparatus, Orsat's 64 

natural 49 

Galloway boiler 8 

Girders 236 

Globe valves 252 

Grate-area 362 

bars 112 

water 1 24 

Grates, rocking 114 

Green's economizer 130, 131 

link grate 122 

Grooving 95 

Gun iron 19 1 

Gusset stays 169, 196 

Hand-holes 5. 3 8 ° 

Hand-riveting 3 2 7 

Hangers for pipe 296 



INDEX. 427 

PAGE 

Hawley down-draught furnace 1 24 

Heat-balance in boiler test 358 

Heat of combustion 50, 51, 52, 56 

(carbon) 53, 54 

calculation of 56 

(fuels) 51 

of the liquid (water) 418 

Heating-surface 6 

of boiler-tubes (table) 416 

value of 150 

Heine attached superheater 39 

boiler 24 

Holmes' furnace 229 

Hollow cylinder 196 

Hoppe's purifier 82 

Horizontal multitubular boiler 2 

Horse-power of boilers 148 

Howden's system 127 

Huston brace 160 

Hydraulic accumulators 325, 326 

riveting-machine 321 

with cam and toggle 326 

test 232 

of boiler 240 

Incomplete combustion, loss from 70 

Independently-fired superheaters 42 

Induced draughts r 25 

Injectors 285 

Iron rods, weight of 4! 5 

Joints in piping 295 

Jones' under-fed stoker 1 22 

Kent's table of chimneys x?-* 

Kerosene oil g^ 

Koerting injector 285 

Laminations jgp 

Lancashire boiler y 

La P 204, 374 

Lap-joints 2 o 5 

with welt 209, 211 

-seam boilers 2 co 



428 INDEX. 

PA«E 

Laying out plates 311 

stays ' 383 

Leavitt boiler 20 

Length of sections 379 

Lever safety-valve 259 

Lewes (marine-boiler scale) . . 84 

Liberty tube-cleaner -. 299 

Life of boilers 246 

Lifting-dogs . ^ . . . 308 

Lignite 48 

Lime-extracting feed-water heater 82 

Limit of elasticity 182 

Link grate, Green's 122 

Lloyd's rules for flues -. 235 

Locke damper regulator 272 

Locomotive-boiler 18 

staying of 162 

type 20 

Logarithms 410 

Longitudinal joint 368 

Mahler's composition of fuels 52 

formula 58 

Malleable iron 192 

Manholes 5, 172, 380 

Manning boilers , 10, n 

Marine boilers 15, 27 

Babcock & Wilcox 27 

proportions of 151 

scale 84-89 

staying of 167 

water-tube 27 

Materials ......... 1 78 

McDaniels trap 274 

Mechanical stokers 116 

American ............. ". 119 

Jones' . '. 1 20 

Roney 117 

Methods of failure of riveted joints 202 

of making boiler tests 333 

of supporting boilers . 173 

of testing plate . * 180, 186 

Mineral impurities . 77 

matter in water (table) .............. 76 

oil 49 



INDEX. 429 

*A<S3 

Modulus of elasticity 182 

Morison's furnace 232 

Natural sines, cos, and tan 414 

trigonometric functions 414 

Naval boilers, proportions of 151 

Nozzles 380 

Oil-burning furnaces 1 24 

filter . . . . 281 

scale 89 

Organic impurities in feed-water 91 

Orsat's gas apparatus 64 

Pancake 89 

Peat 48 

Peet valve 255 

Petroleums, composition of 50 

Pipe, anchor for 296 

arrangement of steam 288-297 

area and size of Appendix 

blow-off 286 

feed 283 

hangers for 296 

size for given horse-power 297 

support for 296 

Pipe-bends, rigidity of 292 

covering 299 

fittings for superheated steam 46 

joints 295 

Piping 288 

Pitch of rivets 205 

Pitting . . . . , 95 

Plain cylindrical boiler 7 

Plan of boiler-shop 305 

Planing-machine 314 

plates . . 314 

Plate, crushing of 204 

lap - - - - -- ....... -. .......... -.--. 204 

P^ner 315 

rolls .............. ..^ ......— .^. . .'. 314 

shearing of 204 

tearing of ..,**....-.....;...... ^ 203 

Pop safety-valve . ... ^ ........ i ;..... ^ ..... ^ ....................... . 263 

Portable riveting-machine *............*... i -.;:.;;...;................ . 3 23 



430 INDEX. 

PAGE 

Power of boilers 1 43 

Power-pump for riveter 324 

Priming . , 373 

Proportions of boilers 151 

Properties of saturated sl:eam 419 

of steel 184 

Prosser tube-expander 328 

Pulsation of steam-pipes 295 

Pumps 284 

Pump for hydraulic riveter 324 

Punch 314 

and holder 310 

for tube-holes 310 

Punched or drilled plates 203, 319 

Purve's furnace 230, 231 

Pyrometers 3 50 

Rate of combustion 1 49 

Reach of a riveting-machine 322 

Reducing- valve 271 

Reduction of area 183 

Return steam-traps 277 

Rigidity of pipe-bends 292 

Ring-seam 373 

Rivet, diameter of 205 

Riveted joints, calculation of 201 

designing 217 

efficiency of 201 

friction of 204 

limitations 221 

methods of failure 202 

Riveting-machines, cam and toggle 321 

hydraulic 321 

with cam and toggle 326 

portable 3 23 

Rivets 191, 199, 200 

pitch of 205 

shearing and crushing 204 

Rocking-grates 114 

Rolls for plate 314 

Roney stoker 117 

Safety-plugs 270 

valves 257 

Sal-ammoniac 81 






INDEX. 431 

PAGE 

Sample boiler test blank 351 

Saving by covering pipes 299 

Scale, marine boiler 84, 89 

Scarfing 314 

Scotch boiler 1 5-17 

Screw-threads (table) 416 

Sea-water, composition of 84 

Segments of circles 412, 413 

Selection of type of boiler ^^, 360 

Semi-bituminous coal 47 

Separator, Curtis 280 

Detroit 281 

Stratton _ 279 

Triumph 280 

Shearing 183 

of rivets 204 

P^tes 204, 313 

Shears 313 

Shop-practice 304 

Size and surface of boiler-tubes 416 

of steam-pipe 297 

Sizes of steam, gas, and water pipe (table) 417 

Smoke-box 6 

prevention 122 

Snap-riveting 327 

Soda 78 

Specific heat 55 

of superheated steam 37, 38 

volumes 55 

Specifications and contract for boiler 392, 394 

for steel 184 

Sphere, strength of 198 

Spherical ends 170 

Split-draught 10 

Stability of chimneys 138 

Stay-bolts 193 

Stay-rods 194, 385 

calculation of 385 

Stayed flat plates 238 

Staying 153, 381 

beneath tubes 160 

(calculation of) 381 

cylindrical tubular boiler 153 

laying out 383 

locomotive-boiler 162 



432 INDEX. 

PAGE 

Staying of marine boiler >68 

Stays, diagonal 195 

Steam-dome 170 

Steam, flow in pipes 298 

flow of 298, 347 

gas, and water pipe (table) 417 

gauges 268 

nozzle 172 

piping 288, 297 

quality of 144 

space 145 

tables 419 

traps, Baird's 275 

Bundy 277 

Curtis 277 

Flynn 276 

McDaniel's 214 

return 277 

Walworth 275 

Steam-pipe pulsations 295 

Steel 184 

specifications for 184 

Stirling attached superheater 39 

boiler 25 

Stokers, mechanical 116 

Strain 182 

Stratton separator •. 279 

Strength of boilers 1 78 

Stress 182 

Stretch limit 182 

Submerged tube-sheet 13, 14 

Sulphate of lime 78 

Sunken tube-sheet . . j 13, 14 

Superheated steam, specific heat of 38 

Superheaters 37 

American 44 

attached 38 

Babcock & Wilcox 38 

Foster 43 

Heine 39 

independently-fired 42 

Stirling 39 

Superheating surface, Manning boiler 13 

Surface blow 9 2 



INDEX. 433 

PAGE 

Table of logarithms 410 

Tables of properties of saturated steam 419 

Tannic acid 81 

Tearing of plate 203 

Temperature of combustion 73 

Test on furnace flues 225-233 

Testing boilers for evaporation '. ^^^ 

Testing-machines 1 78 

Test-pieces 179 

Testing plate, methods of 180, 186 

Thickness of shell 368 

Thornycroft boiler 30 

Throttling calorimeter 342 

Through-stays 2 

Traveling grate 122 

Triumph separator , 280 

Tube-cleaner for soot 301 

Tube-cleaners, Liberty 299 

Weinland 300 

Tube-expanders 3 28 

Tube-holes, drills for 310 

punch for 310 

plates 2 

sheet 362, 376 

sheet, sunken 13, 14 

Tubes - - 362 

after expanding 330 

Two-flue boiler 6 

Type of boiler, selection of t i t )) 360 



Ultimate elongation 183 

strength 182 

Uptake .......... . . . .".' .'.".'.' 2 

area of 379 

U. S. Inspectors' rules for flues 234 

Valves 252 

angle 253 

Chapman 254 

. check 256 

gate 254 

globe 252 

Peet 255 

reducing 271 



434 INDEX. 

PAGE 

Valves, safety, lever 259 

pop 263 

Van Stone joint 295 

Vertical boilers 10-14 

rolls for plate 317 

Vibration of steam pipes 295 

Volume of ton of coal 74 

Volumes, specific 55 

Wainwright feed-water heater 282 

Walworth steam-trap 275 

Wash-out plugs 173 

Water column 266 

grate , 124 

heat of the liquid 418 

leg 18 

level 365 

tube boilers 20 

boiler-setting 105, 106 

marine boilers 27 

weight and volume of (table) 418 

Weinland tube-cleaner 300 

Wheel-draught 9 

William's composition of fuels 51 

Wind pressure 138 

Wood : 49 

Wrought iron 190 

steam, gas, and water pipe 417 

Yarrow boiler 32 

Yield-point 182 

Zinc in boilers 87 



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Lunge's Techno-chemical Analysis. (Cohn)..~ i2mo, 1 00 

* McKay and Larsen's Principles and Practice of Butter-making 8vo, 1 50* 

Maire's Modern Pigments and their Vehicles i2mo, 2 00 

Mandel's Handbook for Bio-chemical Laboratory nmo, 1 50 

* Martin's Laboratory Guide to Qualitative Analysis with the Blowpipe . . nmo, 60 
Mason's Examination of Water. (Chemical and Bacteriological.). . ..i2mo, 1 25 

Water-supply. (Considered Principally from a Sanitary Stan dpi 

8vo, 4 00 

Matthews's Textile Fibres. 2d Edition, Rewritten 8vo, 4 00 

* Meyer's Determination of Radicles in Carbon Compounds. (Tingle). . nmo, 1 25 
Miller's Cyanide Process nmo, 1 00 

Manual of Assaying nmo, 1 00 

Minet's Production of Aluminum and its Industrial Use. (Waldo) nmo, 2 50 

Mixter's Elementary Text-book of Chemistry nmo, 1 50 

Morgan's Elements of Physical Chemistry nmo. 3 00 

Outline of the Theory of Solutions and its Results nmo, 1 00 

* Physical Chemistry for Electrical Engineers 12 mo, 1 50 

Morse's Calculations used in Cane-sugar Factories i6mo, mor, 1 50 

* Muir's History of Chemical Theories and Laws 8vo, 4 00 

Mulliken's General Method for the Identification of Pure Organic Compounds. 

Vol. I Large 8vo, 5 00 

O'Driscoll's Notes on the Treatment of Gold Ores 8vo, 2 00 

Ostwald's Conversations on Chemistry. Part One. (Ramsey") nmo, 1 50 

Part Two. (Turnbull) nmo, 2 00 

* Palmer's Practical Test Book of Chemistry nmo, 1 00 

* Pauli's Physical Chemistry in the Service of Medicine. (Fischer^ nmo, 1 25 

* Penfield's Notes on Determinative Mineralogy and Record of Mineral Tests. 

8vo, paper, 50 
Tables of Minerals, Including the Use of Minerals and Statistics of 

Domestic Production 8vo, 1 00 

Pictet's Alkaloids and their Chemical Constitution. (Biddle) 8vro, 5 00 

Poole's Calorific Power of Fuels 8vo, 3 00 

Prescott and Winslow's Elements of Water Bacteriology, with Special Refer- 
ence to Sanitary Water Analysis nrr.o, 1 50 

* Reisig's Guide to Piece-dyeing. . 8vo, 25 00 

Richards and Woodman's Air, Water, and Food from a Sanitary Standpoint.. 8vo, 2 00 

Ricketts and Miller's Notes on Assaying 8 vo , 3 00 

Rideal's Disinfection and the Preservation of Food 8vo, 4 00 

Sewage and the Bacterial Purification of Sewage 8vo, 4 00 

Riggs's Elementary Manual for the Chemical Laboratory. 8vo, 1 25 

Robine and Lenglen's Cyanide Industry. (Le Clerc) 8vo, 4 00 

Ruddiman's Incompatibilities in Prescriptions , . .8vo, 2 00 

Whys in Pharmacy nmo, 1 00 

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Ruer's Elements of Metallography. (Mathewson) (In Preparation.) 

Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 

Salkowski's Physiological and Pathological Chemistry. (Orndorff) 8vo, 

Schimpf's Essentials of Volumetric Analysis i2mo, 

* Qualitative Chemical Analysis 8vo, 

Text-book of Volumetric Analysis i2mo, 

Smith's Lecture Notes on Chemistry for Dental Students 8vo, 

Spencer's Handbook for Cane Sugar Manufacturers i6mo, mor, 

Handbook for Chemists of Beet-sugar Houses i6mo, mor. 

Stockbridge's Rocks and Soils 8vo, 

* Tillman's Descriptive General Chemistry 8vo, 

* Elementary Lessons in Heat 8vo 4 

Treadwell's Qualitative Analysis. (Hall) „ 8vo s 

Quantitative Analysis. (Hall) 8vo, 

Turneaure and Russell's Public Water-supplies 8vo, 

Van Deventer's Physical Chemistry for Eeginners. (Boltwood) nmo, 

Venable's Methods and Devices for Bacterial Treatment of Sewage 8vo, 

Ward and Whipple's Freshwater Biology. (In Press.) 

Ware's Beet-sugar Manufacture and Refining. Vol. I Small 8vo, 

Vol.11 SmallSvo, 

Washington's Manual of the Chemical Analysis of Rocks 8vo, 

* Weaver's Military Explosives 8vo, 

Wells's Laboratory Guide in Qualitative Chemical Analysis 8vo, 

Short Course in Inorganic Qualitative Chemical Analysis for Engineering 
Students nmo, 

Text-book of Chemical Arithmetic nmo, 

Whipple's Microscopy of Drinking-water 8vo, 

Wilson's Chlorination Process i2mo, 

Cyanide Processes nmo, 

Winton's Microscopy of Vegetable Foods 8vo, 



CIVIL ENGINEERING. 

BRIDGES AND ROOFS. HYDRAULICS. MATERIALS OF ENGINEER- 
ING. RAILWAY ENGINEERING. 

Baker's Engineers' Surveying Instruments 12 mo, 3 00 

Bixby's Graphical Computing Table Paper iq^ v 24} inches. 25 

Breed and Hosmer's Principles and Practice of Surveying. 2 Volumes. 

Vol. I. Elementary Surveying 8vo, 

Vol. II. Higher Surveying 8vo, 

* Burr's Ancient and Modern Engineering and the Isthmian Canal 8vo, 

Comstock's Field Astronomy for Engineers 8vo, 

* Corthell's Allowable Pressures on Deep Foundations nmo, 

Crandall's Text-book on Geodesy and Least Squares 8vo, 

Davis's Elevation and Stadia Tables 8vo, 

Elliott's Engineering for Land Drainage nmo, 

Practical Farm Drainage nmo, 

*Fiebeger's Treatise on Civil Engineering 8vo, 

Flemer's Phototopographic Methods and Instruments 8vo, 

Folwell's Sewerage. (Designing and Maintenance. ) 8vo, 

Freitag's Architectural Engineering 8vo, 

French and Ives's Stereotomy 8vo, 

Goodhue's Municipal Improvements nmo, 

Gore's Elements of Geodesy 8vo, 

* Hauch's and Rice's Tables of Quantities for Prelhrinary Estimates . . nmo, 

Hayford's Text-book of Geodetic Astronomy 8vo, 

Hering's Ready Reference Tables. (Conversion Factors) i6mo, mor. 

Howe's Retaining Walls for Earth 12.no, 

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* Ives's Adjustments of the Engineer's Transit and Level i6mo, Bds. 25 

Ives and Hilts's Problems in Surveying .• i6mo, mor. 1 50 

Johnson's (J. B.) Theory and Practice of Surveying Small 8vo, 4 00 

Johnson's (L. J.) Statics by Algebraic and Graphic Methods 8vo, 2 00 

Kinnicutt, Winslow and Pratt's Purification of Sewage. (In Preparation.) 
Laplace's Philosophical Essay on Probabilities. 'Truscott and Emory) 

i2mo, 2 00 

Mahan's Descriptive Geometry 8vo, 1 50 

Treatise on Civil Engineering. (1873-) (Wood) 8vo, 5 00 

Merriman's Elements of Precise Surveying and Geodesy 8vo, 2 50 

Merriman and Brooks's Handbook for Surveyors i6mo, mor. 2 00 

Nugent's Plane Surveying 8vo, 3 so 

Ogden's Sewer Construction. (In Press.) 

Sewer Design i2mo, 2 00 

Parsons's Disposal of Municipal Refuse 8vo, 2 00 

Patton's Treatise on Civil Engineering 8vo, half leather, 7 50 

Reed's Topographical Drawing and Sketching 4to, 5 00 

Rideal's Sewage and the Bacterial Purification of Sewage 8vo, 4 00 

Riemer's Shaft-sinking under Difficult Conditions. (Corning and Peele). . . 8vo, 3 00 

Siebert and Biggin's Modern Stone-cutting and Masonry 8vo, 1 50 

Smith's Manual of Topographical Drawing. (McMillan). . 8vc, 2 50 

Soper's Air and Ventilation of Subways Large nmo, 2 50 

Tracy's Plane Surveying i6mo, mor. 3 00 

* Trautwine's Civil Engineer's Pocket-book i6mo, mor. 5 00 

Venable's Garbage Crematories in America 8vo, 2 00 

Methods and Devices for Bacterial Treatment of Sewage 8vo, 3 00 

Wait's Engineering and Architectural Jurisprudence 8vo, 6 00 

Sheep, 6 50 

Law of Contracts 8vo, 3 00 

Law of Operations Preliminary to Construction in Engineering and Archi- 
tecture 8vo, 5 00 

Sheep, 5 50 

Warren's Stereotomy — Problems in Stone-cutting .8vo, 2 50 

* Waterbury's Vest-Pocket Hand-book of Mathematics for Engineers. 

2fX 5* inches, mor. 1 00 
Webb's Problems in the Use and Adjustment of Engineering Instruments. 

i6mo, mor. 1 25 

Wilson's (H. N.) Topographic Surveying 8vo. 3 50 

Wilson's (W. L.) Elements of Railroad Track and Construction. (In Press.) 

BRIDGES AND ROOFS. 



Boiler's Practical Treatise on the Construction of Iron Highway Bridges 8vo 
Burr and talk's Design and Construction of Metallic Bridges . . 8vo 

Influence Lines for Bridge and Roof Computations 8vo' 3 01 

Du Bois's Mechanics of Engineering. Vol. II '.'. Small 4 to', 10 00 

Foster's Treatise on Wooden Trestle Bridges 4to ' - 0O 

Fowler's Ordinary Foundations g ' " 

French and Ives's Stereotomy ' „ ' 

Greene's Arches in Wood, Iron, and Stone " 8vo' 

Bridge Trusses g ' 

Roof Trusses ' 

8vo, 1 25 

Grimm's Secondary Stresses in Bridge Trusses 8 vo 2 ' 

Heller's Stresses in Structures and the Accompanying Deformations '.'.".' 8vo ' 

Howe's Design of Simple Roof-trusses in Wood and Steel 8vo* 

Symmetrical Masonry Arches 80' 

Treatise on Arches R ' 

Johnson, Bryan, and Turneaure's Theory and Practice in 'the Designing™/ * °' 

Modern Framed Structures Small 4 to, to 00 

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Merriman and Jacoby's Text-book on Roofs and Bridges: 

Part I. Stresses in Simple Trusses 8vo, 

Part II. Graphic Statics. ; 8vo, 

Part III. Bridge Design 8vo, 

Part IV. Higher Structures 8vo, 

Morison's Memphis Bridge. • Oblong 4to, 

Sondericker's Graphic Statics, with Applications to Trusses, Beams, and Arches. 

8vo, 
Waddell's De Pontibus, Pocket-book for Bridge Engineers ...... i6mo, mor, 

* Specifications for Steel Bridges i2mo, 

Waddell and Harrington's Bridge Engineering. (In Preparation.) 

Wright's Designing of Draw-spans. Two parts in one volume 8vo, 3 50 



HYDRAULICS. 

Barnes's Ice Formation 8vo, 3 00 

Bazin's Experiments upon the Contraction of the Liquid Vein Issuing from 

an Orifice. (Trautwine) 8vo, 2 00 

Bovey's Treatise on Hydraulics 8vo, 5 00 

Church's Diagrams of Mean Velocity of Water in Open Channels. 

Oblong 4to, paper, 1 50 

Hydraulic Motors 8vo, 2 00 

Mechanics of Engineering 8vo, 6 00 

Coffin's Graphical Solution of Hydraulic Problems i6mo, mor. 2 50 

Flather's Dynamometers, and the Measurement of Power nmo, 3 00 

Folwell's Water-supply Engineering 8vo, 4 00 

Frizell's Water-power 8vo, 5 00 

Fuertes's Water and Public Health nmo, 1 50 

Water-filtration Works i2mo, 2 50 

Ganguillet and Kutter's General Formula for the Uniform Flow of Water in 

Rivers and Other Channels. CHering and Trautwine; 8vo, 4 00 

Hazen's Clean Water and How to Get ft Large nmo, 1 50 

Filtration of Public Water-supplies 8vo, 3 oo 

Hazlehurst's Towers and Tanks for Water-works 8vo, 2 50 

Herschel's 115 Experiments on the Carrying Capacity of Large, Riveted, Metal 

Conduits 8vo, 2 00 

Hoyt and Grover's River Discharge 8vo, 2 00 

Hubbard and Kiersted's Water- works Management and Maintenance 8vo, 4 «o 

* Lyndon's Development and Electrical Distribution of Wafer Power. . . .8vo, 3 oo 
Mason's Water-supply. (Considered Principally from a Sanitary Standpoint.) 

8vo, 4 00 

Merriman's Treatise on Hydraulics 8vo, 5 00 

* Michie's Elements of Analytical Mechanics 8vo, 4 00 

* Molitor's Hydraulics of Rivers, Wefrs and Fluices . . 8vo, 2 00 

Schuyler's Reservoirs for Irrigation, Water-power, and Domestic Water- 
supply Large 8vo, 5 00 

* Thomas and Watt's Improvement of Rivers 4to, 6 00 

Tumeaure and Russell's Public Water-supplies 8vo, 5 00 

Wegmann's Design and Construction of Dams. 5th Ed., enlarged ... 4*0, 6 00 

Water-supply of the City of New York from 1658 to 1895 4to, 10 00 

Whipple's Value of Pure Water Large i2mo, 1 00 

Williams and Hazen's Hydraulic Tables 8vo, 1 50 

Wilson's Irrigation Engineering Small 8vo, 4 00 

Wolff's Windmill as a Prime Mover 8vo, 3 00 

Wood's Elements of Analytical Mechanics 8vo, 3 00 

Turbines 8vo - 2 50 

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MATERIALS OF ENGINEERING. 

Baker's Roads and Pavements 8vo, 

Treatise on Masonry Construction. . . . , 8vo» 

Birkmire's Architectural Iron and Steel 3vo, 

Compound Riveted Girders as Applied in Buildings 8vo, 

Black's United States Public Works Oblong 4tQ, 

Bleininger's Manufacture of Hydraulic Cement. (In Preparation.) 

* Bovey's Strength of Materials and Theory of Structures 8vo, 

Burr's Elasticity and Resistance of the Materials of Engineering 8vo, 

Byrne's Highway Construction 8vo, 

Inspection of the Materials and Workmanship Employed in Construction. 

i6mo, 

Church's Mechanics of Engineering 8vo, 

Du Bois's Mechanics of Engineering. 

Vol. I. Kinematics, Statics, Kinetics Small 4to, 7 50 

Vol. II. The Stresses in Framed Structures, Strength of Materials and 

Theory of Flexures Email 4to, 10 00 

♦Eckel's Cements, Limes, and Plasters 8vo, 6 00 

Stone and Clay Products used in Engineering. (In Preparation.) 

Fowler's Ordinary Foundations 8vo, 3 50 

Graves's Forest Mensuration 8vo, 4 00 

Green's Principles of American Forestry nmo, 1 50 

* Greene's Structural Mechanics 8vo, 2 50 

Holly and Ladd's Analysis of Mixed Paints, Color Pigments and Varnishes 

Large r2ino, 2 50 
Johnson's (C. M.) Chemical Analysis of Special Steels. (In Preparation.) 

Johnson's (J. B.) Materials of Construction Large 8vo, 

Keep's Cast Iron 8vo, 

Kidder's Architects and Builders' Pocket-book i6mo, 

Lanza's Applied Mechanics 8vo, 

Maire's Modern Pigments and their Vehicles • . . . i2mo, 

Martens's Handbook on Testing Materials. (Henning) 2 vols 8vo, 

Maurer's Technical Mechanics 8vo, 

Merrill's Stones for Building and Decoration 8vo, 

Merriman's Mechanics of Materials _ 8vo, 

* Strength of Materials « i2mo, 

Metcalf's Steel. A Manual for Steel-users i2mo, 

Morrison's Highway Engineering 8vo, 

Patton's Practical Treatise on Foundations ■ 8vo, 

Rice's Concrete Block Manufacture 8vo, 

Richardson's Modern Asphalt Pavements 8vo> 

Richey's Handbook for Superintendents of Construction i6mo, mor. 

* Ries's Clays: Their Occurrence, Properties, and Uses 8vo, 

Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 

*Schwarz'sLongleafPinem Virgin Forest... I2mo - 

Snow's Principal Species of Wood 8v0 » 

Spalding's Hydraulic Cement • I2m0 » 

Text-book on Roads and Pavements I2mo » 

Taylor and Thompson's Treatise on Concrete, Plain and Reinforced 8vo, 

Thurston's Materials of Engineering. In Three Parts 8vo, 

Part I. Non-metallic Materials of Engineering and Metallurgy 8vo, 

Part n. Iron and Steel 8v0 « 

Part ni- A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents 8vo » 

Tillscn's Street Pavements and Paving Materials 8vo, 

Turneaure and Maurer's Principles of Reinforced Concrete Construction.. 8vo, 
Waterbury»s Manual of Instructions-for the Use of Students in Cement Labora- 
tory Practice. (In Press.) 



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Wood's (De V.) Treatise on the Resistance of Materials, and an Appendix on 

the Preservation of Timber 8vo, 2 00 

Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and 

Steel Svo, 4 00 

RAILWAY ENGINEERING. 

Andrews's Handbook for Street Railway Engineers 3x5 inches, mor. 1 25 

Berg's Buildings and Structures of American Railroads 4to, 5 00 

Brooks's Handbook of Street Railroad Location i6mo, mor. 1 50 

Butt's Civil Engineer's Field-book i6mo, mor. 2 50 

Crandall's Railway and Other Earthwork Tables 8vo, 1 50 

Transition Curve i6mo, mor. 1 50 

* Crockett's Methods for Earthwork Computations. 8vo, 1 50 

Dawson's "Engineering" and Electric Traction Pocket-book i6mo, mor. 5 00 

Dredge's History of the Pennsylvania Railroad: (1879) Paper, 5 00 

Fisher's Table of Cubic Yards Cardboard, 25 

Godwin's Railroad Engineers' Field-book and Explorers' Guide. . . i6mo, mor. 2 50 
Hudson's Tables for Calculating the Cubic Contents of Excavations and Em- 
bankments 8vo, 1 00 

Ives and Hilts's Problems in Surveying, Railroad Surveying and Geodesy 

i6mo, mor. 1 50 

Molitor and Beard's Manual for Resident Engineers i6mo, 1 00 

Nagle's Field Manual for Railroad Engineers i6mo, mor. 3 00 

Philbrick's Field Manual for Engineers i6mo, mor. 3 00 

Raymond's Railroad Engineering. 3 volumes. 

Vol. I. Railroad Field Geometry. (In Preparation.) 

Vol. II. Elements of Railroad Engineering. . Svo, 3 50 

Vol. III. Railroad Engineer's Field Book. (In Preparation.) 

Searles's Field Engineering i6mo, mor. 3 00 

Railroad Spiral i6mo, mor. 1 50 

Taylor's Prismoidal Formulae and Earthwork 8vo, 1 50 

*Trautwine's Field Practice of Laying Out Circular Curves for Railroads. 

i2nio. mor. 2 50 

* Method of Calculating the Cubic Contents of Excavations and Embank- 

ments by the Aid of Diagrams 8vo, 2 00 

Webb's Economics of Railroad Construction Large nmo, 2 50 

Railroad Construction i6mo, mor. 5 00 

Wellington's Economic Theory of the Location of Railways Small 8vo, 5 00 

DRAWING. 

Barr's Kinematics of Machinery 8vo, 2 50 

* Bartlett's Mechanical Drawing 8vo, 3 00 

* " " " Abridged Ed 8vo, 150 

Coolidge's Manual of Drawing 8vo. paper, 1 00 

Coolidge and Freeman's Elements of General Drafting for Mechanical Engi- 
neers Oblong 4to, 2 50 

Durley's Kinematics of Machines 8vo, 4 00 

Emch's Introduction to Projective Geometry and its Applications 8vo, 2 50 

Hill's Text-book on Shades and Shadows, and Perspective 8vo, 2 00 

Jamison's Advanced Mechanical Drawing 8vo, 2 00 

Elements of Mechanical Drawing 8vo, 2 50 

Jones's Machine Design: 

Part I. Kinematics of Machinery 8vo, 1 50 

Part H. Form, Strength, and Proportions of Parts 8vo, 3 00 

MacCord's Elements of Descriptive Geometry. . . 8vo, 3 oc 

Kinematics ; or, Practical Mechanism 8vo, 5 00 

Mechanical Drawing 4to, 4 00 

Velocity Diagrams 8vo, 1 50 

10 



McLeod's Descriptive Geometry Large i2mo, 

* Mahan's Descriptive Geometry and Stone-cutting 8vo, 

Industrial Drawing. (Thompson ) 8vo, 

Moyer's Descriptive Geometry 8vo, 

Reed's Topographical Drawing and Sketching 4to, 

Reid's Course in Mechanical Drawing 8vo, 

Text-book of Mechanical Drawing and Elementary Machine Design. 8vo, 

Robinson's Principles of Mechanism 8vo, 

Schwamb and Merrill's Elements of Mechanism 8vo, 

Smith's (R. S.) Manual of Topographical Drawing. (McMillan) 8vo, 

Smith (A. W.) and Marx's Machine Design 8vo, 

* Titsworth's Elements of Mechanical Drawing Oblong 8vo, 

Warren's Drafting Instruments and Operations i2mo, 

Elements of Descriptive Geometry, Shadows, and Perspective 8vo, 

Elements of Machine Construction and Drawing , . .8vo, 

Elements of Plane and Solid Free-hand Geometrical Drawing i2mo, 

General Problems of Shades and Shadows 8vo, 

Manual of Elementary Problems in the Linear Perspective of Form and 

Shadow i2mo, 

Manual of Elementary Projection Drawing i2mo, 

Plane Problems in Elementary Geometry nmo, 

Problems, Theorems, and Examples in Descriptive Geometry 8vo, 

Weisbach's Kinematics and Power of Transmission. (Hermann and 
Klein) 8vo, 

Wilson's (H. M.) Topographic Surveying 8vo, 

Wilson's (V. T.) Free-hand Lettering 8vo, 

Free-hand Perspective 8vo, 

Woolf's Elementary Course in Descriptive Geometry Large 8vo, 

ELECTRICITY AND PHYSICS. 

* Abegg's Theory of Electrolytic Dissociation, (von Ende) nmo, 

Andrews's Hand-Book for Street Railway Engineering ....3X5 inches, mor. 

Anthony and Brackett's Text-book of Physics. (Magie) Large i2mo, 

Anthony's Lecture-notes on the Theory of Electrical Measurements. . . .nmo, 
Benjamin's History of Electricity 8vo, 

Voltaic Cell 8vo, 

Betts's Lead Refining and Electrolysis 8vo, 

Classen's Quantitative Chemical Analysis by Electrolysis. (Boltwood). .8vo, 

* Collins's Manual of Wireless Telegraphy nmo, 

Mor. 
Crehore and Squier's Polarizing Photo-chronograph 8vo, 

* Danneel's Electrochemistry. (Merriam) nmo, 

Dawson's "Engineering" and Electric Traction Pocket-book . . . .i6mo, mor. 
Dolezalek's Theory of the Lead Accumulator (Storage Battery), (von Ende) 

nmo, 

Duhem's Thermodynamics and Chemistry. (Burgess) 8vo, 

Flather's Dynamometers, and the Measurement of Power nmo, 

Gilbert's De Magnete. (Mottelay ) 8vo, 

* Hanchett's Alternating Currents nmo, 

Hering's Ready Reference Tables (Conversion Factors) i6mo, mor. 

* Hobart and Ellis's High-speed Dynamo Electric Machinery 8vo, 

Holman's Precision of Measurements 8vo, 

Telescopic Mirror-scale Method, Adjustments, and Tests. . . .Large 8vo, 

* Karapetoff's Experimental Electrical Engineering 8vo, 

Kinzbrunner's Testing of Continuous-current Machines 8vo, 

Landauer's Spectrum Analysis. (Tingle) 8vo, 

Le Chatelier's High-temperature Measurements. (Boudouard — Burgess)., nmo, 
Lob's Electrochemistry of Organic Compounds. (Lorenz) 8vo, 

* London's Development and Electrical Distribntion of Water Power 8vo, 

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75 


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* Lyons's Treatise on Electromagnetic Phenomena. Vols. I. and II. 8vo, each, 

* Michie's Elements of Wave Motion Relating to Sound and Light 8vo, 

Morgan's Outline of the Theory of Solution and its Results i2mo, 

* Physical Chemistry for Electrical Engineers i2mo, 

Niaudet's Elementary Treatise on Electric Batteries. (Fishback). . . . i2mo, 

* Norris's Introduction to the Study of Electrical Engineering 8vo, 

* Parshall and Hohart's Electric Machine Design 4to, half mor. 

Reagan's Locomotives: Simple, Compound, and Electric. New Edition. 

Large 12 mo, 

* Rosenberg's Electrical Engineering. (Haldane Gee — Kinzbrunner). .. .8vo, 

Ryan, Norris, and Hoxie's Electrical Machinery. Vol. 1 8vo, 

Swapper's Laboratory Guide for Students in Physical Chemistry i2mo, 

* Tillman's Elementary Lessons in Heat 8vo, 

Tory and Pitcher's Manual of Laboratory Physics Large i2mo, 

Ulke's Modern Electrolytic Copper Refining „ Svo, 

LAW. 

* Davis's Elements ot Law s 8vo, 

* Treatise on the Military Law of United States 8vo, 

* Sheep, 

* Dudley's Military Law and the Procedure of Courts-martial . . . .Large nmo, 

Manual for Courts-martial i6mo, mor. 

Wait's Engineering and Architectural Jurisprudence 8vo, 

Sheep, 

Law of Contracts 8vo, 

Law of Operations Preliminary to Construction in Engineering and Archi- 
tecture 8vc 

Sheep, 

MATHEMATICS. 

Baker's Elliptic Functions 8vo, 

Briggs's Elements of Plane Analytic Geometry. (Bocher) nmo, 

* Buchanan's Plane and Spherical Trigonometry 8vo, 

Byerley's Harmonic Functions 8vo, 

Chandler's Elements of the Infinitesimal Calculus i2rao, 

Compton's Manual of Logarithmic Computations i2mo, 

* Dickson's College Algebra Large nmo, 

* Introduction to the Theory of Algebraic Equations Large i2mo, 

Emch's Introduction to Projective Geometry and its Applications 8vo, 

Fiske's Functions of a Complex Variable 8vo, 

Halsted's Elementary Synthetic Geometry . .8vo, 

Elements of Geometry 8vo, 

* Rational Geometry i2mo, 

Hyde's Grassmann's Space Analysis Svo, 

* Jonnson's (J- B.) Three-place Logarithmic Tables: Vest-pocket size, paper, 

100 copies, 

* Mounted on heavy cardboard, 8X10 inches, 

10 copies, 
Johnson's (W. W.) Abridged Editions of Differential and Integral Calculus 

Large i2mo, 1 vol. 

Curve Tracing in Cartesian Co-ordinates i2mo, 

Differential Equations 8vo, 

Elementary Treatise on Differential Calculus Large i2mo, 

Elementary Treatise on the Integral Calculus Large i2mo, 

* Theoretical Mechanics nmo, 

Theory of Errors and the Method of Least Squares nmo, 

Treatise on Differential Calculus Large i2mo, 

Treatise on the Integral Calculus Large nmo, 

Treatise on Ordinary and Partial Differential Equations. . Large i2mo, 

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Laplace's Philosophical Essay on Probabilities. (Truscott and Emory). .nmo, 2 00 

* Ludlow and Bass's Elements of Trigonometry and Logarithmic and Other 

Tables 8vo, 3 00 

Trigonometry and Tables published separately Each, 2 00 

* Ludlow's Logarithmic and Trigonometric Tables 8vo, 1 00 

Macfarlane's Vector Analysis and Quaternions 8vo, 1 00 

McMahon's Hyperbolic Functions 8vo, 1 00 

Manning's Irrational lumbers and their Representation by Sequences and 

Series i2mo, 1 25 

Mathematical Monographs. Edited by Mansfield Merriman and Robert 

S. Woodward Octavo, each 1 00 

No. 1. History of Modern Mathematics, by David Eugene Smith. 
No. 2. Synthetic Projective Geometry, by George Bruce Halsted. 
No. 3. Determinants, by Laenas Gifford Weld. No. 4. Hyper- 
bolic Functions, by James McMahon. ICo. 5. Harmonic Func- 
tions, by William E. Byerly. No. 6. Grassmann's Space Analysis, 
by Edward W. Hyde. No. 7. Probability and Theory of Errors, 
by Robert S. Woodward. No. 8. Vector Analysis and Quaternions, 
by Alexander Macfarlane. No. 9. Differential Equations, by 
Wiiliam Woolsey Johnson. No. 10. The Solution of Equations, 
by Mansfield Merriman. No. 11. Functions of a Complex Variable, 
by Thomas S. Fiske. 

Maurer'o Technical Mechanics 8vo, 4 00 

Merriman's Method of Least Squares 8vo, 2 00 

Solution of Equations 8vo, 1 00 

Rice and Johnson's Differential and Integral Calculus. 2 vols, in one. 

Large i2mo, 1 50 

Elementary Treatise on the Differential Calculus Large i2mo, 3 00 

Smith's History of Modern Mathematics 8vo, 1 co 

* Veblen and Lennes's Introduction to the Real Infinitesimal Analysis of One 

Variable 8vo, 2 00 

* Waterbury's Vest Pocket Hand-Book of Mathematics for Engineers. 

2-g- X 5s inches, mor. 1 00 

Weld's Determinations 8vo, 1 co 

Wood's Elements of Co-ordinate Geometry 8vo, 2 00 

Woodward's Probability and Theory of Errors 8vo, 1 00 



MECHANICAL ENGINEERING. 
MATERIALS OF ENGINEERING, STEAM-ENGINES AND BOILERS. 

Bacon's Forge Practice nmo, 1 50 

Baldwin's Steam Heating for Buildings i2mo, 2 50 

Bair's Kinematics of Machinery 8vo, 2 50 

* Bartlett's Mechanical Drawing 8vo, 3 00 

* " " " Abridged Ed 8vo, 150 

Benjamin's Wrinkles and Recipes nmo, 2 00 

* Burr's Ancient and Modern Engineering and the Isthmian Canal 8vo, 3 50 

Carpenter's Experimental Engineering 8vo, 6 00 

Heating and Ventilating Buildings 8vo, 4 00 

Clerk's Gas and Oil Engine Large i2mo, 4 00 

Compton's First Lessons in Metal Working i2mo, 1 50 

Compton and De Groodt's Speed Lathe i2mo, 1 50 

Coolidge's Manual of Drawing 8vo, paper, 1 00 

Coolidge and Freeman's Elements of General Drafting for Mechanical En- 
gineers Oblong 4to 

Cromwell's Treatise on Belts and Pulleys , . -. i2mo, 1 

Treatise on Toothed Gearing i 2 mo, 

Durley's Kinematics of Machines 8vo, 

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50 

1 50 

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Flather's Dynamometers and the Measurement of Power. i2mo, 

Rope Driving „ i2mc, 

Gill's Gas and Fuel Analysis for Engineers , i2mo, 

Goss'."> Locomotive Sparks 8vo, 

Greene's Pumping Machinery. (In Preparation.) 

Hering's Ready Reference Tables (Conversion Factors) i6mo, mor. 

* Hobart and Ellis's High Speed Dynamo Electric Machinery 8vo, 

Hutton's Gas Engine. „ Svo, 

Jamison's Advanced Mechanical Drawing 8vo, 

Elements of Mechanical Drawing 8vo, 

Jones's Machine Design: 

Part I. Kinematics of Machinery 8vo, 

Part II. Form, Strength, and Proportions of Parts 8vo, 

Kent's Mechanical Engineers' Pocket-book i6mo, mor. 

Kerr's Power and Power Transmission 8vo, 

Leonard's Machine Shop Tools and Methods' 8vo, 

* Lorenz's Modern Refrigerating Machinery. (Pope, Haven, and Dean) . . . 8vo, 
MacCord's Kinematics; or, Practical Mechanism 8vo, 

Mechanical Drawing '..... 4to, 

Velocity Diagrams 8vo, 

MacFar land's Standard Reduction Factors for Gases 8vo, 

Mahan's Industrial Drawing. (Thompson) 8vo, 

* Parshall and Hobart's Electric Machine Design Small 4to, half leather, 

Peele's Compressed Air Plant for Mines 8vo, 

Poole's Calorific Power of Fuels 8vo, 

* Porter's Engineering Reminiscences, 1855 to 1882 8vo, 

Reid's Course in Mechanical Drawing 8vo, 

Text-book of Mechanical Drawing and Elementary Machine Design. 8vo, 

Richard's Compressed Air nmo, 

Robinson's Principles of Mechanism 8vo, 

Schwamb and Merrill's Elements of Mechanism 8vo, 

Smith's (O.) Press- working of Metals 8vo, 

Smith (A. W.) and Marx's Machine Design 8vo, 

Sorel ' s Carbureting and Combustionin Alcohol Engines . (Woodward and Preston) . 

Large 12 mo, 
Thurston's Animal as a Machine and Prime Motor, and the Laws of Energetics. 

nmo, 
Treatise on Friction and Lost Work in Machinery and Mill Work... Svo, 

Tillson's Complete Automobile Instructor i6mo, 

mor. 

* Titsworth's Elements of Mechanical Drawing Oblong 8vo, 

Warren's Elements of Machine Construction and Drawing 8vo, 

* Waterbury's Vest Pocket Hand Book of Mathematics for Engineers. 

2? XSf inches, mor. 
Weisbach's Kinematics and the Power of Transmission. (Herrmann — 

Klein) 8vo, 

Machinery of Transmission and Governors. (Herrmann — Klein).. .8vo, 
Wood's Turbines. 8vo, 

MATERIALS OF ENGINEERING. 

* Bovey's Strength of Materials and Theory of Structures 8vo, 7 50 

Burr's Elasticity and Resistance of the Materials of Engineering 8vo, 7 50 

Church's Mechanics of Engineering 8vo, 6 00 

* Greene's Structural Mechanics 8vo, 2 50 

Holley and Ladd's Analysis of Mixed Paints, Color Pigments, and Varnishes. 

Large nmo, 2 50 

Johnson's Materials of Construction „ 8vo, 6 00 

Keep's Cast Iron 8vo, 2 50 

Lanza's Applied Mechanics 8vo, 7 50- 

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Maire's Modern Pigments and their Vehicles nmo, 2 00 

Martens's Handbook on Testing Materials. (Henning) 8vo, 7 50 

Maurer's Technical Mechanics 8vo, 4 00 

Merriman's Mechanics of Materials 8vo, 5 00 

* Strength of Materials nmo, 1 00 

Metcalf 's Steel. A Manual for Steel-users nmo, 2 00 

Sabin's Industrial and Artistic Technology of Paints and Varnish 8vo, 3 00 

Smith's Materials of Machines nmo, 1 00 

Thurston's Materials of Engineering 3 vols., 8vo, 8 00 

Parti. Non-metallic Materials of Engineering and Metallurgy .. .8vo, 2 00 

Part II. Iron and Steel 8vo, 3 50 

Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents 8vo, 2 50 

Wood's (De V.) Elements of Analytical Mechanics 8vo, 3 00 

Treatise on the Resistance of Materials and an Appendix on the 

Preservation of Timber 8vo, 2 00 

Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and 

Steel 8vo, 4 00 



STEAM-ENGINES AND BOILERS. 

Berry's Temperature-entropy Diagram nmo, 1 25 

Carnot's Reflections on the Motive Power of Heat. (Thurston) nmo, 1 50 

Chase's Art of Pattern Making nmo, 2 50 

Creighton's Steam-engine and other Heat-motors ... .Svo, 5 00 

Dawson's "Engineering" and Electric Traction Pocket-book i6mo, mor. 5 00 

Ford's Boiler Making for Boiler Makers i8mo, 1 00 

Gebhardt's Steam Power Plant Engineering. (In Press.) 

Goss's Locomotive Performance .... 8vo, 5 00 

Hemenway's Indicator Practice and Steam-engine Economy nmo, 2 00 

Hutton's Heat and Heat-engines 8vo, 5 00 

Mechanical Engineering of Power Plants 8vo, 5 00 

Kent's Steam boiler Economy 8vo, 4 00 

Kneass's Practice and Theory of the Injector 8vo, 1 50 

MacCord's Slide-valves Svo, 2 00 

Meyer's Modern Locomotive Construction 4to, 10 oc 

Moyer's Steam Turbines. (Tn Press.) 

Peabody's Manual of the Steam-engine Indicator nmo 5 1 50 

Tables of the Properties of Saturated Steam and Other Vapors 8vo, 1 00 

Thermodynamics of the Steam-engine and Other Heat-engines 8vo, 5 00 

Valve-gears for Steam-engines 8vo, 2 50 

Peabody and Miller's Steam-boilers 8vo, 4 00 

Pray's Twenty Years with the Indicator Large 8vo, 2 5c 

Pupin's Thermodynamics of Reversible Cycles in Gases and Saturated Vapors. 

(Osterberg) nmo, 1 25 

Reagan's Locomotives: Simple, Compound, and Electric. New Edition. 

Large nmo, 3 50 

Sinclair's Locomotive Engine Running and Management nmo, 2 00 

Smart's Handbook of Engineering Laboratory Practice nmo, 2 50 

Snow's Steam-boiler Practice 8vo, 3 00 

Spangler's Notes on Thermodynamics nmo, 1 00 

Valve-gears , 8vo, 2 50 

Spangler, Greene, and Marshall's Elements o Steam-engineering 8vo, 3 00 

Thomas's Steam-turbines .... 8vo, 4 00 

Thurston's Handbook of Engine and Boiler Trials, and the Use of the Indi- 
cator and the Prony Brake 8vo, 5 00 

Handy Tables 8vo, 1 50 

Manual of Steam-boilers, their resigns, Construction, and Operation.. 8vo, 5 00 

15 



Thurston's Manual of the Steam-engine 2 vols., 8vo, 10 00 

Part I. History, Structure, and Theory 8vo, 6 00 

Part II, Design, Construction, and Operation 8vo, 6 00 

Steam-boiler Explosions in Theory and in Practice nmo,. 1 50 

Wehrenfenning's Analysis and Softening of Boiler Feed-water (Patterson) 8vo, 4 00 

Weisbach's Heat, Steam, and Steam-engines. (Du Bois) 8vo, 5 00 

Whitham's Steam-engine Design 8vo, 5 00 

Wood's Thermodynamics, Heat Motors, and Refrigerating Machines. ..8vo, 4 00 

MECHANICS PURE AND APPLIED. 

Church's Mechanics of Engineering . . .8vo, 6 00 

Notes and Examples in Mechanics 8vo, 2 00 

Dana's Text-book of Elementary Mechanics for Colleges and Schools. .i2mo, 1 50 
Du Bois's Elementary Principles of Mechanics : 

Vol. I. Kinematics 8vo, 3 50 

Vol. II. Statics 8vo, 4 00 

Mechanics of Engineering. Vol. I Small 4to, 7 50 

VoL H. Small 4to, 10 00 

♦•Greene's Structural Mechanics 8vo, 2 50 

James's Kinematics of a Point and the Rational Mechanics of a Particle. 

Large i2mo, 2 00 

* Johnson's (W. W.) Theoretical Mechanics nmo, 3 00 

Lanza's Applied Mechanics ; 8vo, 7 50 

* Martin's Text Book on Mechanics, Vol. I, Statics nmo, 1 25 

* Vol. 2, Kinematics and Kinetics . .i2mo, 1 50 
Maurer's Technical Mechanics 8vo, 4 00 

* Merriman's Elements of Mechanics nmo, 1 00 

Mechanics of Materials 8vo, 5 00 

* Michie's Elements of Analytical Mechanics 8vo, 4 00 

Robinson's Principles of Mechanism 8vo, 3 00 

Sanborn's Mechanics Problems Large nmo, 1 50 

Schwamb and Merrill's Elements of Mechanism 8vo, 3 00 

Wood's Elements of Analytical Mechanics ." 8vo, 3 00 

Principles of Elementary Mechanics nmo, 1 25 

MEDICAL. 



* Abderhalden's Physiological Chemistry in Thirty Lectures. (Hall and Defren) 

8vo, 
von Behring's Suppression of Tuberculosis. (Bolduan) nmo, 

* Bolduan's Immune Sera nmo, 

Davenport's Statistical Methods with Special Reference to Biological Varia- 
tions i6mo, mor. 

Ehrlich's Collected Studies on Immunity. (Bolduan) 8vo, 

* Fischer's Physiology of Alimentation .Large nmo, cloth, 

de Fursac's Manual of Psychiatry. (Rosanoff and Collins) Large nmo, 

Hammarsten's Text-book on Physiological Chemistry. (Mandel) 8vo, 

Jackson's Directions for Laboratory Work in Physiological Chemistry. ..8vo, 

Lassar-Cohn's Practical Urinary Analysis. (Lorenz), nmo, 

Mandel's Hand Book for the Bic-Chemical Laboratory nmo, 

* Pauli's Physical Chemistry in the Service of Medicine. (Fischer) nmo, 

' Pozzi-Escot's Toxins and Venoms and their Antibodies. (Cohn) nmo, 

Rostoski's Serum Diagnosis. (Bolduan) nmo, 

Ruddiman's Incompatibilities in Prescriptions 8vo, 

Whys in Pharmacy nmo, 

Salkowski's Physiological and Pathological Chemistry. (Orndorff) 8vo, 

* Satterlee's Outlines of Human Embryology nmo, 

Smith's Lecture Notes on Chemistry for Dental Students 8vo, 

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Steel's Treatise on the Diseases of the Dog 8vo, 3 50 

* Whipple's Typhoid Fever Large nmo, 3 00 

Woodhull's Notes on Military Hygiene i6mo, 1 50 

* Personal Hygiene nmo, 1 00 

Worcester and Atkinson's Small Hospitals Establishment and Maintenance, 

and S ggestions for Hospital Architecture, with Plans for a Smalt 

Hospital nmo, 1 25 

METALLURGY, 

Betts's Lead Refining by Electrolysis 8vo, 4 00 

Bolland's Encyclopedia of Founding and Dictionary of Foundry Terms Used 

in the Practice of Moulding nmo, 

Iron Founder nmo, 

" " Supplement nmo, 

Douglas's Untechnical Addresses on Technical Subjects nmo, 

Goesel's Minerals and Metals: A Reference Book i6mo, mor. 

* Iles's Lead-smelting nmo, 

Keep's Cast Iron 8vo, 

Le Chatelier's High-temperature Measurements. (Boudouard — Burgess) 1 2mo, 

Metcalf's Steel. A Manual for Steel-users nmo, 

Miller's Cyanide Process nmo, 

Minet's Production of Aluminium and its .Industrial Use. (Waldo) . . .nmo, 

Robine and Lenglen's Cyanide Industry. (Le Clerc) : .8vo, 

Ruer's Elements of Metallography. (Mathewson) (In Press.) 

Smith's Materials of Machines nmo, 

Thurston's Materials of Engineering. In Three Parts 8vo, 

Part I. Non-metallic Materials of Engineering and Metallurgy . . . 8vo, 

Part II. Iron and Steel 8vo, 

Part HI. A Treatise on Presses, Bronzes, and Other Alloys and their 

Constituents Svo, 

Ulke's Modern Electrolytic Copper*Refining 8vo, 

West's American Foundry Practice nmo, 

Moulder's Text Book nmo, 

Wilson's Chlorination Process nmo, 

Cyanide Processes nmo, 

MINERALOGY. 

Barringer's Description of Minerals of Commercial Va'.ue Oblong, mor. 

Boyd's Resources of Southwest Virginia 8vo, 

Boyd's Map of Southwest Virginia. . . Pocket-book form. 

* Browning's Introduction to the Rarer Elements Svo, 

Brush's Manual of Determinative Mineralogy. (Penfield) 8vo, 

Butler's Pocket Hand-Book of Minerals i6mo, mor. 

Chester's Catalogue of Minerals 8vo, paper, 

Cloth, 

* Crane's Gold and Silver 8vo, 

Dana's First Appendix to Dana's New " System of Mineralogy. ." . .Large 8vo, 

Manual of Mineralogy and Petrography nmo 

Minerals and How to Study Them nmo, 

System of Mineralogy Large Svo, half leather, 

Text-book of Mineralogy 8vo > 

Douglas's Untechnical Addresses on Technical Subjects nmo, 

Eakle's Mineral Tables 8vo > 

Stone and Clay Froducts Used in Engineering. (In Preparation.) 

E°-leston's Catalogue of Minerals and Synonyms 8vo, 

Goesel's Minerals and Metals: A Reference Book i6mo, mor. 

Groth's Introduction to Chemical Crystallography (Marshall) nmo, 

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* Iddings's Rock Minerals gvo, 5 00 

Johannsen's Determination of Rock-forming Minerals in Thin Sections 8vo, 4 00 

* Martin's Laboratory Guide to Qualitative Analysis with the Blowpipe. i2tno, 60 
Merrill's Non-metallic Minerals: Their Occurrence and Uses 8vo, 4 00 

Stones for Building and Decoration 8vo, 5 00 

* Penfield's Notes on Determinative Mineralogy and Record of Mineral Tests. 

8vo, paper, 50 
Tables of Minerals, Including the Use of Minerals and Statistics of 

Domestic Production 8vo, 1 00 

* Pirsson's Rocks and Rock Minerals i2mo, 2 50 

* Richards's Synopsis of Mineral Characters.. i2mo, mor. 1 25 

* Ries's Clays: Their Occurrence, Properties, and Uses 8vo, 5 00 

* Tillman's Text-book of Important Minerals and Rocks 8vo , 2 00 

MINING. 

* Beard's Mine Gases and Explosions Large nmo, 3 00 

Boyd's Map of Southwest Virginia. Pocket-£ook form 2 00 

Resources of Southwest Virginia 8vo, 3 00 

* Crane's Gold and Silver 8vo, 5 00 

Douglas's Untechnical Addresses on Technical Subjects nmo 1 00 

Eissler's Modern High Explosives , 8vo, 4 00 

Goesel's Minerals and Metals : A Reference Book i6mo, mor. 3 00 

Ihlseng's Manual of Mining 8vo, 5 00 

* Iles's Lead-smelting nmo, 2 50 

Miller's Cyanide Process nmo, 1 00 

O'Driscoll's Notes on the Treatment of Gold Ores Svo, 2 00 

Peele's Compressed Air Plant for Mines 8vo, 3 00 

Riemer's Shaft Sinking Under Difficult Conditions. (Corning and Peele) . . .8vo, 3 «o 

Robine and Lenglen's Cyanide Industry. (Le Clerc) .8vo, 4 00 

* Weaver's Military Explosives 8vo, 3 00 

Wilson's Chlorination Process nmo, 1 so 

Cyanide Processes nmo, 1 50 

Hydraulic and Placer Mining. 2d edition, rewritten i2mo s 2 50 

Treatise on Practical and Theoretical Mine Ventilation 12 mo, 1 25 

SANITARY SCIENCE. 

Association of State and National Food and Dairy Departments, Hartford Meeting, 

1906 8vo, 3 00 

Jamestown Meeting, 1907 8vo, 3 00 

* Bashore's Outlines of Practical Sanitation nmo, 1 25 

Sanitation of a Country House 1 2mo, 1 00 

Sanitation of Recreation Camps and Parks nmo, 1 00 

Folwell's Sewerage. (Designing, Construction, and Maintenance) 8vo, 3 00 

Water-supply Engineering 8vo, 4 00 

Fowler's Sewage Works Analyses nmo, 2 00 

Fuertes's Water-filtration Works nmo, 2 50 

Water and Public Health nmo, 1 50 

Gerhard's Guide to Sanitary House-inspection i6mo, 1 00 

* Modern Baths and Bath Houses 8vo, 3 00 

Sanitation of Public Buildings nmo, 1 50 

Hazen's Clean Water and How to Get It Large nmo, 1 50 

Filtration of Public Water-supplies 8vo, 3 00 

Kinnicut, Winslow and Pratt's Purification of Sewage. (In Press.) 

Leach's Inspection and Analysis of Food with Special Reference to State 

Control 8vo, 7 00 

Mason's Examination of Water. (Chemical and Bacteriological) nmo, 1 25 

Water-supply. (Considered Principally from a Sanitary Standpoint) . . 8vo, 4 00 
18 



* Merriman's Elements of Sanitary Engineering 8vo 2 00 

Ogden's Sewer Design . .". .'.7.'.7.7.7i2mo! 2 00 

Parsons's Disposal of Municipal Refuse 8vo 2 00 

Prescott and Winslow's Elements of Water Bacteriology, with Special Referl 

ence to Sanitary Water Analysis I2mo - - Q 

* Price's Handbook on Sanitation '/' " I2mo ' x ^ Q 

Richards's Cost of Food. A Study in Dietaries! i 2mo ' 1 00 

Cost of Living as Modified by Sanitary Science . . I2mo ' j 00 

Costof Shelter . . .7. .. .'lamo! 1 00 

* Richards and Williams's Dietary Computer 8vo, 1 50 

Richards and Woodman's Air, Water, and Food from a Sanitary Stand- 

P° int 8vo, 2 00 

Rideal's Disinfection and the Preservation of Food 8vo, 400 

Sewage and Bacterial Purification of Sewage 8vo,' 4 00 

Soper's Air and Ventilation of Subways Large i 2 moi 2 50 

Turneaure and Russell's Public Water-supplies 8vo' 5 00 

Venable's Garbage Crematories in America 8vo,' 2 00 

Method and Devices for Bacterial Treatment of Sewage 8vo', 3 00 

Ward and Whipple ' s Freshwater Biology . (In Press. ) 

Whipple's Microscopy of Drinking-water 8vo 3 50 

* T yP hod Fever .'.' .Large' iimo' 3 00 

Value of Pure Water Large I2mo x Q0 

Winslow's Bacterial Classification. (In Press.) 

Winton's Microscopy of Vegetable Foods. .• g v0> 7 _ 

MISCELLANEOUS. 

Emmons's Geological Guide-book of the Rocky Mountain Excursion of the 

International Congress of Geologists Larf e 8vo, 1 50 

Ferrel's Popular Treatise on the Winds 8vo' 4 00 

Fitzgerald's Boston Machinist ".".*.*.".".". i8mo' 1 00 

Gannett's Statistical Abstract of the World ' / 24mo ' ^ 

Haines's American Railway Management i2mo', 2 50 

* Hanusek's The Microscopy of Technical Products. (Winton) .......... . 8vo,' 5 00 

Ricketts's History of Rensselaer Polytechnic Institute 1 824-1394. 

Large 12 mo, 3 00 

Rotherham's Emphasized New Testament. . . . s Large 8vo 2 00 

Standage's Decoration of Wood, Glass, Metal, etc "." i 2 mo' 2 00 

Thome's Structural and Physiological Botany. (Bennett) i6mo' 2 25 

Westermaier's Compendium of General Botany. (Schneider) .8vo] 2 00 

Winslow's Elements of Applied Microscopy \12tr 0, 1 50 

HEBREW AND CHALDEE TEXT-BOOKS. 

Green's Elementary Hebrew Grammar i2mo 1 2s 

Gesenius's Hebrew and Chaldee Lexicon to the Old Testament Scr.ptures! 

(Tregelles) SmaU 4 to : half mor! 5 00 



OCT 39 1903 



